I read in a post last night that using Regular Unleaded Fuel rather than Premium was fine as long as you weren't gunning the engine. My question is as an alternative unsing Regular Unleaded and adding 105 Octane Booster rather than Premium what could you expect and is this advised?

Black Cat

 

Black Cat, first off, welcome to the Forums. I think you will find that we are full of knowledge and are willing to pass it on to other people. We are also a friendly bunch. So, we do ask that you stop by the "New Member" section and introduce yourself. You will quickly learn who the movers and shakers are around here. So, grab yourself a cup of joe, sit back and enjoy.

As for using regular gas, that has been a mixed blessing. In short, since you are in Maryland and at sea level, you are more likely to have issues than someone that lives at high altitudes. I'm south of you in California, MD. So, that is not looking good in the way of using a lower octane gas.

As for using a bottle of octane booster. First off, they may call it "105 Octane", but you are looking at a very minimal gain in octane rating. I seem to recall it only boosting about 0.5 or less. So, do not even bother with buying that product. Secondly, a bottle of that stuff runs what, about $6? Lets see, the difference between regular and premium near me is $0.33 a gallon. So, even if I ran the car next to empty and put a full 14 gallons into the car, I am only spending $4.62 a tank full using premium over running regular. Take out the fact of spending $6 on a bottle of octane booster, I still save $1.50 or so each fill up at a minimum. I do not see how this is beneficial. Even at $0.40 a gallon difference between regular and premium, you are still breaking even if not still saving some.

I do not want to burst your bubble. But, for the little bit extra that it costs to keep premium in the car and not risk damage to the engine, it is a small price to pay in my book. You damage the engine, how many tank fulls of gas would you have to run through the car to make up that difference. If you make the assumption that you spent $1000 on the repair from running the lower grade gas and you saved $5 a tankful, that is 200 tanks. At roughly 300 miles a tank, that is 60,000 miles. That is a lot of driving to make up that difference.

 

My wife used my 2.5 liter and thought she would do me a favour, not knowing to use premium, filled up my tank with regular. It ran like crap & the gas mileage decresed significantly. Save yourself some grief and put the good stuff in your Jag !

 

Thanks for the replies guy's, I've heard this before but never asked anyone.

Black Cat

 

I would question the safer use of regular at higher altitudes if the vehicle is supercharged. A forced intake air engine will show less altitude affect than one of natural aspiration. I'm not sure which engine type the OP has.

 

I tried Regular one time on mine since I've read of members that have success with regular, and My Car did NOT like it at all, I felt the difference right away, and my MPG dropped quite a bit also.

So I decided to go Premium all the way and it just feels right.

 

All Stock for now 3.0 V6

Black Cat

 

i used mid-grade for about 3 months then switched to premium. The small bump in octane (89 for mid / 93 premium) has also bumped my rating up about 2 MPG.

 

The cost of adding bottle after bottle of octane booster would outweigh the cost of just buying high octane gas in the first place. Whether your car NEEDS high octane or not is a different question. Older, pre-computerized cars occasionally suffered from detonation (pinging/knocking) during acceleration if the fuel was too low of an octane rating. In extreme cases this caused severe engine damage. Today's cars, like your X-type have knock sensors that automatically retard the ignition timing long before any damage can occur. The driver might notice reduced full-throttle power or lower gas mileage these are the exceptions.

There is no other difference between low and high octane gas than resistance to detonation.

 

Definitely agree, i put in regular one time and could not wait to get that crap out of my system!!!! the car sputtered and overall produced very poor gas mileage unfortunately i filled the tank so i had to wait a few hundred miles.

 

If you read the car's manual it recommends to use 94 octane.

My family had a 2000 excursion and my dad always put high-test (94 octane) in the car.

He learned years later that the suv requires 83 octane (low test) and pistons on the v10 could have blown off due to the higher octane.

As a rule of thumb, check your manual.

I would also use high test in anything that requires gas, ex: lawn mower, leaf blower, etc. Because of ethanol. Now that gas has 10% ethanol it water downs the gas a bit. It actually caused my lawnmower to crap out from low-test.

Use high octane.
In new york we are fortunate enough to have 93. When I lived in Newport Beach California I only found 91 octane to be the highest. In south carolina they have 94 octane, can't find 94 in new york.

~Kory

 

I'm having this dilemma now in deciding whether to switch to 87/89 or stay at 91/93 because I just bought a 14gal tank to keep at my house and fill the cars and bike when needed. One car runs 87, the Jag X-type normally runs 91/93, and the bike normally runs 91/93. Now I have heard that the bike can handle 87/89 no problem so now I'm wondering if the Jag can handle it too. That way I can just load up the fuel container with 87/89 and not worry about wasting money when the wife decides not to go to the gas station because we have gas at home.

So I have a 2002 Jaguar X-type 3.0 Auto . Does it REQUIRE high-octane or is it merely Recommended?

 

There's umpteen discussions on this very question if you search. The unfortunate side of it is sifting through the myths and misunderstandings of what's being said. Read my answer above if you want one persons' opinion.

 

nootherids, since you live down near sealevel, the need for the higher octane gas is going to be more likely the situation. Some members have been able to run the low octane fuels and not have any issues. Other members with identical cars have tried to run mid grade gas and had tons of troubles. What you will have happen is hard to say. You car is designed around having advanced timing to help making more power from the engine. This causes you to need to run a fuel that needs a retarder to prevent pre-detonation (ie, knocking). Yes, the computer will attempt to minimize it, but like any mechanical thing, it can only adjust but so far. The question comes, if your motor starts knocking, can it bring the timing back far enough to clear the knocking condition? If it can't, then you can damage the car. If it can, then you simply suffer from loss of some power.

If you are dead set on trying to run a lower grade gas, I would tell you to try running the car to near empty, then put in like half a tank of say mid grade gas from the same station you normally use. See how the car runs. After about 50 miles, you should have a pretty good idea of what the car is going to run like. Do not be surprised if you see a 1 mpg loss in mileage. This is due to you wanting to have the same power as running premium, so, you are having to use more gas to get the same power output.

 

i run 87 octane since i bought the car ...it runs mint in my x

 

Don't get why people bother themselves with low octane gasoline usage and we see a new thread about it almost every month.

The engine was designed to be run on Premium gasoline. Period. Why everybody tries to be a "smart-a#s"?

Thermo, I'm really surprised how patient and calm you're every time you're explaining simple things to grown ups.

 

Nardo, I try to be what I want others to be like. I guess I am "old school" in that I firmly believe "if you want others to act like an adult, you have to be one first". Like I kinda eluded to, every car is different. Some will tolerate it very well. Others, they want the best that they can get. maybe it was the fact that the car rolled off the assembly line on a monday vice a friday. Who knows. I am not quite sure why things happen the way that they do. Sometimes you have to lay it out there to see what happens. Trust me, I am one of those people that has no problems pushing the limits and seeing what can be done. My truck I think proves that (97 Ford Expedition with a 4" lift only, yet still capable of running 37" mud tires). Besides, I also see it as "how do I want to be treated, so I should treat them the same way". I do not try to be better than others, I just know that there is a time and a place to raise the cane.

 

Thermo...thank you!

Others... Read my questions "So I have a 2002 Jaguar X-type 3.0 Auto . Does it REQUIRE high-octane or is it merely Recommended?"

All I needed to know was one of two words: recommended or required. Sure I could've pulled out the manual myself but I figured great members like Thermo would chime in with personal knowledge and experience regarding this particular car. Apparently, it has hurt some cars and other cars haven't suffered at all. Being that my car is about 105k miles and I want to keep it running as long as possible I don't think I want to chance it.

Thanks again to those who provided constructive feedback.

 

Didn't know any of this, so thanks.

 

For those that want a more scientific explanation as to why our cars need premium fuel, read on. If you are not really interested, then skip the rest.

When our motors were designed, they were built with a high compression engine (10.5:1, vice a more standard motor being in the 9.0:1 to 9.5:1 range, where this ratio is the volume of the cylinder with the piston all the way down to the volume of the cylinder with the piston all the way up). Why this is important in getting more power out of the car is that with higher compression engines (assuming all else is equal), the more you compress the fuel/air, the less volume you have. The less volume you have, the quicker this volume can be ignited and all the energy from burning the fuel can be released. Keep in mind that it takes a finite amount of time for the spark to occur and then the flame to travel across the cylinder. Now, we are only talking but maybe 0.001 seconds for this to occur, but it is still an amount of time that engineers have to take into account. The issue comes with an effect known as spontaneous ignition (some call it "dieseling" when it comes to gasoline engines). This is a condition that is created when you change the pressure inside of an enclosed space that also contains a burnable substance (in this case, fuel). If you start changing the pressure at rates greater than 150 psi/sec, the fuel can ignite with no spark present. What you are seeing is essentially the gas molecules are getting slammed together and they are rubbing on each other, forming heat, which then leads to the break down of the burnable substance because of the heat, resulting in combustion when it is not desired. You can experience this effect by taking your hands and putting them together. Now, with your hands just touching, rubbing them across each other (ie, this would be a "low compression" condition). They will get a little warm, but not that bad. Now, do the same thing, but pressing your hands together really good. Where octane plays into this is that it acts like a binder/glue to the gasoline molecules. If the octane can hold the gasoline molecules together to withstand higher pressure change rates, the gasoline is not going to break down and experience the "dieseling".

I mentioned earlier how cars at higher elevations can tolerate the lower grade gasolines better is that at higher elevations, the air is thinner. Because you have less air making it into the cylinder, when you compress the air, you have less there, so, the pressure doesn't rise as fast, therefore the conditions for "dieseling" are not there. Another way to look at it also is when you hear about guys adding turbos and/or superchargers to their vehicles, they find they have to run higher grade gasolines. Because you are forcing more air into the cylinder, when you start compressing the air, the pressure changes are much more dramatic. Hence why you will find that a lot of force aspiration motors run a low compression.

Hopefully this gives people a little insight to how the world around them works. There is much more that can go into this topic. I am just skimming the top to help explain why we have to do what we do.