Sorry if I offended anyone by downgrading off brand cheap gas. Jaguar engines are designed to run on specific gas types be it octane or whatever! Saving a couple of cents using lower octane and/or "no-name" gas is the height of foolishness. Pay now or pay later! Believe it or not... stop being picky about not mentioning octane! Take the advice or leave it. I have the name of a great Jaguar mechanic who would love to meet you and your checkbook.

 

No offence taken on my part and it goes without saying that poor quality gas should not be used in a Jag or any other motor. I was just reiterating the point that octane levels have no connection to 'quality'. The words 'premium gas' refers to octane, not quality.

The original poster was asking specifically about using lower octane fuel in his car, not lower quality fuel.

 

I believe he got onto the topic because I posted about octane levels and timing adjustments and also mentioned how people who have the tendency to do things like that to save money, are also willing to save a penny by crossing the street to get off brand gas worth much less than a penny less. I was mentioning all of these since, like I said, people who have a tendency to do one, also do another. I wanted to include them all so I could recommend against them all.

 

Sidescrollin has valid points, a little harsh at first, but good points! " you recovered beautifully"!. My x gf would want me to drive around the parking lot 10 times to get the closes spot. Call the cell company about 13 cents! After 10 years ! Burned out on that stuff. Hey, moneys tight, but when it comes to my Jag, Id use newspaper for toilet paper to get high test!

 

Have to add, never driven a six, and know nothing about the motors.
BUT, i admitted to myself long ago, I can't keep my foot out out of the 12! Just not going to happen!

 

the smoothness really is intoxicating. Its not about the speed, its the electric feeling of the wheels simply spinning faster and the car just being forced forwards.

I guess the main point here is : if you want good gas mileage, don't drive a v12 jaguar. That is it. If it is worth it to you to pay for gas, thats all there is. If you need good mpgs, go buy a fiat 500.

I am a college student with very little money and I literally pull up to the pump and swipe my card, hit the premium button, and put however much I want in. I have to use it anyway.

I have seen too many "adults" stress over mpg's and which gas station is cheapest to allow it to affect my life. I have to drive to work and i have to drive to class.That is how it is. I need it.

 

Personally I'm like you, Sidescrollin. I virtually never give any particular attention to gas prices (not since I gave up boating years ago, at least. But that's a different story from a different life ). Price is just another thing to worry about that I don't need. I'm a chronic worrier about my kids but, beyond that, I strive to keep my life as concern free as possible. And, besides, gas prices are beyond my 'circle of control'. If something is beyond my circle of control I try to eliminate it from my 'circle of concern'. But, I'm straying....


As to this thread more broadly....


We all have our different hot buttons ...or 'non hot' buttons. The ability to use lower octane fuel is apparently of some importance to Afterburner. From post #1 we know that he is willing to sacrifice some engine efficiency in order to use lower octane fuel and that, by mentioning retarding the timing, has some concept of protecting the engine....so he has given the matter some thought. Perhaps more thought than some of us.

There have been some dire predictions as though engine damage absolutely WILL occur, 'bring your checkbook to your Jag mechanic', etc. Even a posting about stuck-open fuel injectors ...which obviously isn't an octane issue.

In actuality, with the model of Jaguar in question, the idea of running lower octane fuel isn't all *that* crazy or far-fetched, for reasons I already mentioned: The knock sensors will retard the timing when/if pinging occurs and return to the normal timing map when it doesn't. Depending (strongly) on driving style and conditions it is possible to save some money on gas (for those who want to do so), not cause any engine damage, and lose engine efficiency only occasionally.

Anyhow.....

When it comes to my Jags I prefer to save money in other ways than octane rating (some of which others would attribute to me being an idiot, no doubt) but to each his own.

Ramble switch 'off' for the moment

Cheers
DD

 

I also think the "send it to the mechanic" idea is a bit dire. But I think the point in some of the posts is to point out his value in cheaper gas from lower octane may be flawed and he should perhaps evaluate his reasoning.

Regardless if it can be done, the money saved may not exist once all variables are thrown in or is so little he should reconsider whether it is worth it.

 

The key being the price spread between regular (87) and super (91) fuel. I happen to live in an area where the local stations love to have price wars, so we sit on our hands and wait till the price drops then shuttle the fleet off to the pumps for a fill up. That's very nice- but they only discount the regular (87) fuel and not the higher grades.

These intermittent price wars varies the price differential from a low of 5 cents to a high of 14 cents per litre, which is around 50 cents per US gallon. The temptation NOT to use 91 fuel is of course much higher with this sort of potential savings and unless it can be demonstrated that some of sort of harm will befall the vehicle, many will choose the lower priced fuel.

It happens that there is no demonstrable fuel consumption difference in my S-type if I switch from 91 to 87 and as is well known, any detonation is taken care of automatically by the knock sensors. I can detect no loss of performance during normal driving. As such, I have very little incentive to use 91 fuel.

I bought a used SUV last fall equipped with the same 4.6L 4V engine as found in the Ford Mustang. The owners manual and the fuel filler door had the usual warnings to use 'premium' fuel only. In cleaning out the glove box after purchase, I found a pile of old gas receipts each of which showed the owner filling up with 87 octane. A quick phone call revealed that the previous owner had thought that premium meant 'national name brand' and in fact went out of his way to use only 'top tier' fuel. He had no knowledge of octane ratings and added that he had used 87 for the 100K KM he had driven the vehicle.

I use the vehicle to tow a rather bulky boat and trailer. The all up weight combined with the hills around here would cause me to presume that this would set the stage for some serious detonation events so I have used only the prescribed 91 octane so far.

 

I used to live near 2 stations that did that. I quickly found these wars were correlated with a heavy degradation in fuel quality at these two stations ( though this is obviously isn't always the case).

It only lasted a few months until the smaller station, which was instigating the price wars, closed because Shell has a lot more to back itself up with financially.

 

Don't know why you would use an icon from the unhappy deck.

Maybe the previous owner just followed your lead and came to the same conclusions. Runs fine on 87, 87 is cheaper, buy 87. You can't really fault him for the thought process can you? The possibility that you were going to tow with full GVW would have been in the future during his custodianship.

Have you found his 710 receipts from Jiffy Lube?

 

How did you determine that?

 

Jagfixer answered my question (first reply) The logic of my question was why buy a fuel unnecessarily if another fuel will work as well. That was an information request. Since I hadn't owned a Jaguar in 20 years and fuel grades have changed I wanted to insure that I would not be cutting into my milk and french fry budget with an unnecessary expendature
Most of all I enjoyed reading your Doctorial dissertation on fuel grades and purchase locations and I now know I should use premium fuel from an upscale filling station

I am now in the process of buying a 1993 XJS coupe and have a choice of 15" Jaguar wheels (the ones with the ***** cat in the hub) and 16" BBS wheels that look close to the Jaguar wheels. Neither are wire spoked. Please illuminate me with your brilliance on this subject.
Thanks
Reheat

 

Go with the 16" wheels. It's very hard to find decent 15" tires these days.

And, as far as I know....someone might jump in to correct me.... the '93 XJS won't have the knock sensors previously mentioned and that you'd find on a 95-96 model....so be careful!


Cheers
DD

 

Thanks DD
Non critical responses with euridite information makes for pleasant reading. I admire your philosophy of life. "If you can't change it, go with the flow!" So true.
Never thought of tire availability; that was a very good point. I was looking at devaluation of the car and speedometer corrections
Back in the seventies and eighties I owned four Jags. Two XKE's and two XJ's. One six and one double six. Ran them all on regular and never had a bit of trouble. Only the occasional knock when I lowered the hammer. Things change in 30 and 40 years (it seemed like 20 years)

 

Personally I think BBS rims are period-correct and add to the car rather than taking away from it.

 

I think this is the definitive answer to my gas question: Wish I had found it sooner.
Test Results

Thanks for the info on the wheels; I think I will go with the BBS

 

That article does contain some interesting results. Keep in mind that minor variations in dyno results, as stated in the article, are normal variations from test to test and not indicative of 'real' changes in power levels.

In addition to the vehicles mentioned in one of my posts above, I also have an older Corvette with a high compression 'old school' engine with no computer controls. To achieve full performance without encountering detonation, I have to use 91 AKI fuel. I have been caught short once or twice where I was low on fuel and there was only 87 available. It was reasonably easy to avoid problems by keeping the revs up in each gear (not lugging the engine) and just taking it easy when accelerating.

Not sure about any particular Jag, but detonation is very easy to hear in the cabin of the Corvette when I get too adventurous.

 

because i didn't always get gas there, but sometimes I did because the price was so low. If I went across the street to BP I had no issues, but my car ran like crap if I bought gas at those stations. I put some in my uncles super beetle and it was even more obvious because the carb already wasn't set right.

I know what bad gas feels like.Been around enough cars that sat and have put enough "bad gas" into my dad's m38 which then ran fine, to know its gas related.

 

"Our tests confirm that for most cars there is no compelling reason to buy more expensive fuel than the factory recommends"

"Cheapskates burning regular in cars designed to run on premium fuel can expect to trim performance by about the same percent they save at the pump."

thats what ALL of us have been saying. Why did you ignore everyone and require a car and driver article to believe this?

You are making it too black and white "can I or can I not use regular octane". Yes it WORKS, but its bad for the engine. It wasn't designed this way and a "loss in performance" means a whole lot more than a change in 0-60 time.