MPG question?
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From: Pittsburgh, Pa
MPG question?
1998 jag VDP 44,000 miles: changed spark plugs and just put in K&N air filter in place of stock filter ( filter housing still the same ) what should mileage I be getting around town on average? Original sticker says 17 mpg city 22 highway
Also if 87 octane or 89 is used vs 93 what effect will that have?
Last what else can be done to up the fuel economy if any?
Also if 87 octane or 89 is used vs 93 what effect will that have?
Last what else can be done to up the fuel economy if any?
Popular Reply
Mar 28, 2013, 12:26 PM
Senior Member
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From: SoCal
It's true,...Costco and EVERYONE else gets the gas from the same refineries (there is only so many of them in the nation), and that's NOT the issue here.
The issues are, what happens at the "rack", and at the pumps!
1. Consistency of the octane rating
2. Ethanol percentage
3. Filtration system at the pumps
4. Addittives that are added at the retailers "rack", before the gas is loaded on the tanker truck
All five "majors" have the same (or VERY similar) control system, mandated by the company (and the State!), and checked FREQUENTLY (it's a cut throat competition, and no brand wants to be labeled as "inconsistent"!!). Octane rating is very consistent (means: if you are buying 91, you are getting MINIMUM 91). Most of the "bulk resellers" (like Costco), are exempt from the State control, and don't have any of their own!.
The filtration at the pumps is MANDATED at MINIMUM 10 micron (some run 5 micron filters, as I was), and checked weekly (slow, dirty pumps are ordered to replace the filters). When you pump at the truck stops, 7/11s etc. you sometimes experience a VERY slow flow - dirty filters! But,....at least they have them! Arco, Trifty, Costco, Walmart, etc....don't have ANY regulations concerning filtration and octane rating (if you experience the pump going really fast,....chances are, there are no filters in the pumps)! If a gas station owner runs restrictive filters (10 micron or less), he will have to change them more frequently, which dips into his "poolmargin", and he makes less money! If you have no filters, you can sell the gas cheaper (and you wouldn't believe what kind of crap is cleaned out of the underground storage tanks every year!!).
The addittives are not present in the "non-major" gas (you are all familiar with "Techron" that Chevron advertises?). These addittives are NOT a gimmick. They help the combustion, and keep the injectors and valves clean.
But,.....as usual, there is no "free lunch"!! If you buy cheaper gas, you are "saving" money at the pump, but you will have to buy the injector cleaners more often, fuel filters for your car, and you WILL get poorer gasmileage.
Another thing worth mentioning is Ethanol.
If you do some research, you will find that the independent studies in CA, found some retailers blending more than 20%+ ethanol (a whole new subject here!) (10% is MAX allowed!), and their tested octane rating was substandard.
I am not here to argue with anyone. I don't want to offend any gasoline retailer, but all this information is available to anyone on the web. If you don't want to spend time on this research, you can do a simple thing......without relaying on the car computer, fill the tank at the major station, and write down the mileage. Go back to the same station and top it off at any time, and use the calculator to tell you what is your real gas mileage. And then repeat it with a "non-major" station, and you WILL see that the major brand is giving you better mileage. Then you have to ask yourself how much will the fuel filter replacement, injector cleaner, etc. cost you (plus the loss of the gas mileage!), and decide whether is saving 10 cents per galon at the cheaper retailer worth it to YOU. If it is,.....go ahead, and pump whatever you want! This is still somewhat "free" country!
Last edited by danielsand; Mar 28, 2013 at 12:28 PM.
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From: Florida
My 2003 XJ8 gets about 20 mpg on the average -- my trip odometer says so! I average (again, according to the trip meter) about 40-45 mph over the last 4,000 plus miles. When I'm on the highway, I average in the mid 20s.
I always run 93 octane in my car so I can't give you an answer to your question about running lower octane fuel.
My best gas mileage is obtained at around 65-75 mph on the highway. I can suck a lot of gas around town if I drive aggressively.
I always run 93 octane in my car so I can't give you an answer to your question about running lower octane fuel.
My best gas mileage is obtained at around 65-75 mph on the highway. I can suck a lot of gas around town if I drive aggressively.
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From: Virginia Beach, VA
I always use 93 octane also. I get between 15-17 mpg generally, but that is averaging about 20 MPH. There isn't much to do to get better mileage except, tire pressure, air filter, spark plugs and the big one - keep a light foot on the accelerator !
Joined: Oct 2009
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From: Perth Ontario Canada
The K&N filter will do nothing for fuel economy. At full throttle it's difficult to find an advantage so at tiny throttle openings typical of cruising there is NO difference.
What octane rating fuel does Jag recommend for your car? If it's 91 like later years, there's nothing to be gained by going higher. Going lower may lead to reduced engine power output due to the timing being automatically retarded to avoid detonation which in turn may lead to lower mileage. YMMV, as always.
What octane rating fuel does Jag recommend for your car? If it's 91 like later years, there's nothing to be gained by going higher. Going lower may lead to reduced engine power output due to the timing being automatically retarded to avoid detonation which in turn may lead to lower mileage. YMMV, as always.
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Joined: Feb 2013
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From: plantersville, tx
My 1999 XJ8L gets very simular mpg as Oldmike. On extended highway rides I can get up to about 24 mpg. City driving really drags it down. My commute to work is about 1/4 highway and 3/4 city driving for 25 miles. I average about 19 mpg. That is really driving easy with occasional burst to pass some idiot that cant seem to drive the speed limit. This car has really changed my driving habits. I used to drive either full throttle or full brake. Now I take it nice and easy and enjoy the ride.
My 98 XJ8L 4.0 averages 23+ mpg, but that's UK gallons, no idea what that equates to in US gallons. Certainly town driving and short journeys are a disaster mpg-wise, on a long motorway journey cruising at 75 or so, it's around 27mpg.
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From: Bloomington, IL
i get the same as JimmyL, and with there being a 20 cent difference between 87 and 93, i dont think twice about using higher octane, no need to dumb down the engine you know.
Mikey not all places have 91, here in Michigan its 87-89-93 so i obviously have no choice other then 93
Mikey not all places have 91, here in Michigan its 87-89-93 so i obviously have no choice other then 93
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Joined: Oct 2009
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From: Perth Ontario Canada
Far from it, unless someone wants to compare a dirty crudded up OEM filter with a new K&N.
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From: SoCal
My 98 VDP (87K miles), gets 19,5 average (city and freeway combined), with average speed of 33mph (all this according to the OBC). I use the highest octane available in CA (91) exclusively. it has the best average with Mobil gas, and the worse with 76.
As a former gasoline retailer, I know better than pumping anything except MAJOR brands in my cars (no Costco, USA, Valero, Arco, 7/11, Trifty....just to mention some CA "non majors").
As a former gasoline retailer, I know better than pumping anything except MAJOR brands in my cars (no Costco, USA, Valero, Arco, 7/11, Trifty....just to mention some CA "non majors").
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From: Costa Mesa, CA
Hey Danielsand,
Whats up with Costco gas? My wife is partial to saving that .98 for a full tank by driving $2.00 out of the way to pump it. I would LOVE to give her a good reason to stop doing that. (she somehow doesn't see the flawed logic in wasting gas to save a few cents.)
Whats up with Costco gas? My wife is partial to saving that .98 for a full tank by driving $2.00 out of the way to pump it. I would LOVE to give her a good reason to stop doing that. (she somehow doesn't see the flawed logic in wasting gas to save a few cents.)
Joined: Oct 2009
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From: Perth Ontario Canada
I think if someone were to do a bit of research, you'd find that Costco gets their gas from the same refineries as all the majors. The allegations that they sell 'low quality' fuel are groundless.
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From: California, USA
When I still had my Harley, I tried different fuels in it, Always Premium. The motor was highly built up, so minor differences in fuel made a Big difference in performance. I found that Chevron Premium was the best for me. I also found that Costco was the WORST. The bike bucked and coughed until that tank ran out and was replaced. It could have been a fluke and they got water into their system or something, but I've never bought fuel from them since.
76 was also VERY poor running in the Bike. I remember being quite surprised because I figured they'd be one of the top.
After finding Chevron to be the best, I'd ride a few miles out of my way to find it. Although, on a bike, you are always looking for a reason to ride further, much like a Jaguar.
76 was also VERY poor running in the Bike. I remember being quite surprised because I figured they'd be one of the top.
After finding Chevron to be the best, I'd ride a few miles out of my way to find it. Although, on a bike, you are always looking for a reason to ride further, much like a Jaguar.
Last edited by SuperSport; Mar 28, 2013 at 12:02 PM.
Senior Member
Joined: Oct 2012
Posts: 856
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From: SoCal
It's true,...Costco and EVERYONE else gets the gas from the same refineries (there is only so many of them in the nation), and that's NOT the issue here.
The issues are, what happens at the "rack", and at the pumps!
1. Consistency of the octane rating
2. Ethanol percentage
3. Filtration system at the pumps
4. Addittives that are added at the retailers "rack", before the gas is loaded on the tanker truck
All five "majors" have the same (or VERY similar) control system, mandated by the company (and the State!), and checked FREQUENTLY (it's a cut throat competition, and no brand wants to be labeled as "inconsistent"!!). Octane rating is very consistent (means: if you are buying 91, you are getting MINIMUM 91). Most of the "bulk resellers" (like Costco), are exempt from the State control, and don't have any of their own!.
The filtration at the pumps is MANDATED at MINIMUM 10 micron (some run 5 micron filters, as I was), and checked weekly (slow, dirty pumps are ordered to replace the filters). When you pump at the truck stops, 7/11s etc. you sometimes experience a VERY slow flow - dirty filters! But,....at least they have them! Arco, Trifty, Costco, Walmart, etc....don't have ANY regulations concerning filtration and octane rating (if you experience the pump going really fast,....chances are, there are no filters in the pumps)! If a gas station owner runs restrictive filters (10 micron or less), he will have to change them more frequently, which dips into his "poolmargin", and he makes less money! If you have no filters, you can sell the gas cheaper (and you wouldn't believe what kind of crap is cleaned out of the underground storage tanks every year!!).
The addittives are not present in the "non-major" gas (you are all familiar with "Techron" that Chevron advertises?). These addittives are NOT a gimmick. They help the combustion, and keep the injectors and valves clean.
But,.....as usual, there is no "free lunch"!! If you buy cheaper gas, you are "saving" money at the pump, but you will have to buy the injector cleaners more often, fuel filters for your car, and you WILL get poorer gasmileage.
Another thing worth mentioning is Ethanol.
If you do some research, you will find that the independent studies in CA, found some retailers blending more than 20%+ ethanol (a whole new subject here!) (10% is MAX allowed!), and their tested octane rating was substandard.
I am not here to argue with anyone. I don't want to offend any gasoline retailer, but all this information is available to anyone on the web. If you don't want to spend time on this research, you can do a simple thing......without relaying on the car computer, fill the tank at the major station, and write down the mileage. Go back to the same station and top it off at any time, and use the calculator to tell you what is your real gas mileage. And then repeat it with a "non-major" station, and you WILL see that the major brand is giving you better mileage. Then you have to ask yourself how much will the fuel filter replacement, injector cleaner, etc. cost you (plus the loss of the gas mileage!), and decide whether is saving 10 cents per galon at the cheaper retailer worth it to YOU. If it is,.....go ahead, and pump whatever you want! This is still somewhat "free" country!
Last edited by danielsand; Mar 28, 2013 at 12:28 PM.
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From: Florida
That's a good run-down of what the difference is between the lower cost stations and the higher ones. Everyone "knows" that they all get their gas from the same places, but few know why you "should" buy at the more expensive places. I normally get my gas at Shell or Mobil since they carry 93 octane (actually, I haven't been to Shell for a while, but I do know that Mobil has 93). I shy away from the bargain stations, if for no other reason than my peace of mind.
Thanks for the great write-up.
Thanks for the great write-up.
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From: USA, CA
Here in California the highest oct we can buy is 91. I have tested a number of different fuels not just in my XJ8 but also my Camaro and found Chevron to be the best in performance and in mileage. Danielsand is right in his statements. I have a friend who owns 5 stations here in California and has told me the same things. Its no coincidence that Chevron fuel performs better and costs a bit more. Thats all I use now unless I'm traveling and don't have a choice.
Joined: Oct 2009
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From: Perth Ontario Canada
I am not here to argue with anyone. I don't want to offend any gasoline retailer, but all this information is available to anyone on the web. If you don't want to spend time on this research, you can do a simple thing......without relaying on the car computer, fill the tank at the major station, and write down the mileage. Go back to the same station and top it off at any time, and use the calculator to tell you what is your real gas mileage. And then repeat it with a "non-major" station, and you WILL see that the major brand is giving you better mileage. Then you have to ask yourself how much will the fuel filter replacement, injector cleaner, etc. cost you (plus the loss of the gas mileage!), and decide whether is saving 10 cents per galon at the cheaper retailer worth it to YOU. If it is,.....go ahead, and pump whatever you want! This is still somewhat "free" country!
Please explain to me how one brand of gasoline instantly gets better mileage than another- but compare apples to apples by discussing either pure gas or E10. Additives have no direct affect on mileage in the short term.
I've been using whatever brand of gas is at hand and the cheapest if there's a choice and never seen 1 mpg difference in one brand to another, nor any difference in performance.
I have never used any additives nor do any of my vehicles exhibit any signs of need. Unless there's some major difference between the US and Canada in how gasoline is regulated, I think the stories are just that- stories. If any of this were true- where are all the people that have suffered damage to their cars? Why isn't there a public outcry pointing fingers of shame at Costco?
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From: California, USA
That's all very nice but is just repeating old generic myths that have been around for decades. Half the people here say that Brand X is the best and Brand Y is crap. The other half say the opposite.
Please explain to me how one brand of gasoline instantly gets better mileage than another- but compare apples to apples by discussing either pure gas or E10. Additives have no direct affect on mileage in the short term.
I've been using whatever brand of gas is at hand and the cheapest if there's a choice and never seen 1 mpg difference in one brand to another, nor any difference in performance.
I have never used any additives nor do any of my vehicles exhibit any signs of need. Unless there's some major difference between the US and Canada in how gasoline is regulated, I think the stories are just that- stories. If any of this were true- where are all the people that have suffered damage to their cars? Why isn't there a public outcry pointing fingers of shame at Costco?
Please explain to me how one brand of gasoline instantly gets better mileage than another- but compare apples to apples by discussing either pure gas or E10. Additives have no direct affect on mileage in the short term.
I've been using whatever brand of gas is at hand and the cheapest if there's a choice and never seen 1 mpg difference in one brand to another, nor any difference in performance.
I have never used any additives nor do any of my vehicles exhibit any signs of need. Unless there's some major difference between the US and Canada in how gasoline is regulated, I think the stories are just that- stories. If any of this were true- where are all the people that have suffered damage to their cars? Why isn't there a public outcry pointing fingers of shame at Costco?
As far as other stations are concerned, I did use them all for a prolonged period of time to find the difference, and there was a difference. My brothers both did the same. We tried the experiment on a bike trip to Canada and back. We ALL felt a noticeable difference with Chevron, and we all have run it since.
In my opinion, if my bike ran better on a certain brand, then I can only assume it was also getting better mileage. Also again, my bike was heavily modified, so maybe the difference would not be noticed as much in a stock vehicle.
One more thing I noticed on my Mercedes 500SL.. When I ran Regular and not premium from Chevron, the car didn't act much different. But, when I ran regular from Safeway, it was MUCH different. Coughed and Sputtered quite a bit.
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From: on-the-edge
1998 jag VDP 44,000 miles: changed spark plugs and just put in K&N air filter in place of stock filter ( filter housing still the same ) what should mileage I be getting around town on average? Original sticker says 17 mpg city 22 highway
Also if 87 octane or 89 is used vs 93 what effect will that have?
Last what else can be done to up the fuel economy if any?
Also if 87 octane or 89 is used vs 93 what effect will that have?
Last what else can be done to up the fuel economy if any?
Using a fuel rated at less than the recommended octane rating risks detonation.
It also increases the volume of fuel used per mile. This can be observed through ODB-II diagnostics as an increase in Long Term Fuel Trim. The meaning of LTFT is the amount of fuel added to the expected fuel map to achieve the designed fuel to air ratio while the car is running.
This factor must be included in any real world decision about fuel economy as your real concern is *miles per dollar*. So, you have to look at MPG on each octane and convert that using the $/gallon factor as there are differences in cost.
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From: on-the-edge
The issues are, what happens at the "rack", and at the pumps!
1. Consistency of the octane rating
2. Ethanol percentage
3. Filtration system at the pumps
4. Addittives that are added at the retailers "rack", before the gas is loaded on the tanker truck
That is not myth, it is what actually occurs in the real world. As an industry insider, he is quite a bit more familiar with the processes than most readers on the board.
Please explain to me how one brand of gasoline instantly gets better mileage than another- but compare apples to apples by discussing either pure gas or E10.
But, that is not the same gas you buy at the retail pump. You cannot buy that gas at the pump. Nor has the gas been handled the same. See 1 through 4 above.
Additives have no direct affect on mileage in the short term.
I've been using whatever brand of gas is at hand and the cheapest if there's a choice and never seen 1 mpg difference in one brand to another, nor any difference in performance.
I have never used any additives nor do any of my vehicles exhibit any signs of need. Unless there's some major difference between the US and Canada in how gasoline is regulated, I think the stories are just that- stories. If any of this were true- where are all the people that have suffered damage to their cars? Why isn't there a public outcry pointing fingers of shame at Costco?
In summary, it is not a brand x versus brand y battle. It is the fact that brand x versus brand y are somewhat different animals. Raw apples versus apple pie.
The recipes differ, the cooks differ, the storage differs and the serving staff differs.
You can even buy two slices of apple pie at two different eateries. However, one was made from leftover apples, by a slob who took a dump without washing his hands, left in the display case for three weeks because the place is so bad it had no customers until you walked in. Or, buy a slice at a bakery where the baker really cares about his craft, ingredients and product.
The stomach will pretty much tell you tell you that there really is a difference between them. But, you would have a hard time saying they were not both "apple pie" in your apples to apples comparison. And after all, one slice was $0.50 cheaper and you didn't have to leave a tip.
Shell and Costco start with apples, but add different ingredients of different qualities, with different degrees of care and expertise. Unless of course you are about to claim that Costco somehow knows as much about gasoline chemistry as Shell/Exxon and have the same degree of vertical integration.
BTW, at the time of writing there are 181 views of this thread and the thanks button has been clicked 6 times. All of them on the post by DanielSand.
