The OP asked about actane grades and nowhere in the bunch of responses has anyone pointed out that there are several ways to grade octane. I believe in the US, all pump posted octane numbers are so called "AKI" and it is usually about 2 to 3 points lower than the "RON" numbers used in the rest of the world , for the same gasoline. So, the basic statement thatm the X-308 recommended fuel is 93 octane is misleading. It is RON 93, I believe, which equates to AKI 91.

Ethanol discussions, like several others, are quite interesting in that they bring out the "experts" relating the doom and failure stories unlike most other topics. It does give good indication of how little many people truly understand the difference between coincidence, correlation, and causality, and the science of logic.
IF, ethanol does actually degrade gasoline's storage life, it still has little application to operation in a car, unless we are referring to museum pieces, which most XJ8s are not. And IF small engine's gasoline is degraded with time because of lack of air seal in the fuel system, then it has no relation to Jaguars either- just try cracking your fuel cap and drive a few miles-see the CEL!

The other similar topic is engine oil and additives and the recommended frequency of changing it!
And for some reason, Jaguars are supposedly particularly susceptible to these problems!

 

Yes, there's RON, MON, and AKI (RON+MON/2, the commonly used method in the U.S.).

I blame you if a thread starts on ZDDP in motor oil, etc., and I have to pull out my SAE and ILSAC specs to knock down the misinformation!! ;-)

Brian

 

This is true and the confusion between the various octane ratings systems has scuttled more than one discussion on this board.

What also confuses is the various names given fuel around the world- super, premium, five star, ultra, etc. with no standardized rating behind them.

Given that the OP is in the US and referred to using '87' it was a reasonable assumption that the AKI reference number was being used. Just to add to confusion, AKI is also sometimes called PON for pump octane number.

Jaguar themselves is not innocent- they frequently specify octane requirements in North American owners manuals using the RON system which has not been used here since the mid-70s.

Typical fuels today (including Satan Ethanol) have an 8 point spread between the MON and RON ratings. Given the formula for determining AKI or PON, this would mean that a 93 RON fuel would be 89 on the AKI scale.

 

Aw, Brian.
Actually, I love a good oil argument. Its fun to see how passionate folks are about the snake oil they put in, or believe someone else put in for them!

 

I still think this is one of the most brilliant bits of television ever.

 

I have just watched this, it's one I don't recall seeing before....Brilliant, I saw what you did there!!. Allan

 

I try to use jaguar recommended everything and if they say 93 or better I don't question that. I assume they tried and tested their cars when building them. The little extra is insignificant in the overall running costs.
I use premium fuel in other cars as well as the cost is offset in better economy. Although this result can vary on the brand of fuel used. Our premium has NO ethanol. Each to their own I guess. I also use TCW3 additive but thats another story!

 

HOLD ON, NEIL!
You say "I try to use jaguar recommended everything"
and then you say "I also use TCW3 additive"
So Jaguar recommends TCW3???

Jaguar recommendations would be considered to be what to use in its entirety. You can't claim it both ways. Well, obviously you can, since you did, but you shouldn't!

 

Has anybody actually checked their owners manual for what Jaguar recommends? 93AKI is not commonly available in North America as compared to 91.

 

As I posted earlier, it is 91 AKI that is recommended. Thats one of the things I love about a fuel / octane/ ethanol thread. Everybody gets all excited and forgets to even look at the original question!!!

 

91 AKI is 95 RON, not 93.

 

Well, if that's the case, I wonder where folks come up with a 93 octane recommndation. The manual is unambiguous for North Amewrican cars- 91 AKI octane, up to 10 ethanol, or up to 5% methanol with corrosion inhibitors, or up to 15% MTBE.

And, the manual SPECIFICALLY states that if a good grade of gasoline is used, no snake oil ( or maybe it says additives) is needed.

So, for the purists, thats what the manual states and any other "recommendation" without a specific basis is just a personal opinion, no matter what your brother in law who has pumped gas for 75 years thinks!

 

Your right Sparkenzap...Maybe TCW3 wasn't around when Jag printed my manual but I am sure they would have included it if it was available. Being Nicasil they weren't aware of the possible failure of the lining.
If there is a slight chance that by using it may prolong the engine life (at very little cost) I am willing to concede your point. But the exhaust sounds great,I wonder why it deepens the note?
Our petrol pumps in Oz are clearly marked with the RON of 83-87-95-100 Makes it easy!
One litre of 87 is $1.49 and 96 is $1.53 to-day. (LPG was $0.73)

 

I really didn't want to get in on this thread, but...what?

83 & 87 RON, is that a Victorian thing? Sydney you get 91, 91E10 or 98. If you go to United you can get E85 and 100 RON if you want. What the hell can run on 83 RON anyway? That would see just about any modern engine ping it's head off.

 

Well, maybe they would. On the other hand, they would have had to validate that it did not do anything bad to the catalytic convertors. And "I've run it for 20,000 miles and it hadn't bothered them yet" ,won't work! I admit I even used 2 stroke TCW3 while breaking in my new valve job. I am very reluctant to continue, since I sure would hate to have to buy new cats. I did not hear the roar, but if there really is one, one POSSIBLE explanation is something going on in the cats.

I had not heard of TCW3 as a Nikasil failure deterent. I thought it helped valves. My Nikasil engines are both doing fine with 200,000 plus miles.

When I see some real explanation of exactly what and how TCW3 does its magic, then I will believe it might be of value. Right now, the "results" I have seen have been anecdotal. I would love a reference to real data and explanation.

 

Two stroke outboard motor oil has been around for decades, long before these cars were built. Why on earth would Jaguar or any OEM specify that such an oil be mixed with the fuel in a four stroke engine?

There is no credible evidence that using such an oil at 500:1 ratio would have any positive effect on a Nikasil engine.

 

E10 ethanol has only become ubiquitous in the US in the past 10 years. Most fuel has had up to 5% ethanol since the early 80's, especially in colder climates, but the problems only start to show up in higher concentrations. Any non-flex-fuel car made prior to about 2004-2005 will almost certainly not have fuel system seals designed specifically to be used with concentrations of ethanol higher than 3-5%, and ethanol concentrations higher than that do prematurely wear these seals. It's not going to instantly turn the seals to mush, but 10% ethanol does degrade these seals faster than 5% ethanol does unless the material of the seal is specifically formulated to be ethanol resistant.

And at the same octane rating, E10 fuel DOES have less energy content per mass than E0. Simple fact, the energy content of ethanol is less than that of gasoline, therefore the energy content of the fuel is lower, and you will get less mileage per gallon out of E10 than you will out of E0 at the same octane rating. The E10 will provide slightly less power. But due to subsidies, E10 can be significantly cheaper than E0. So it's up to you on a case by case basis to determine if the marginally increased mileage and performance of the E0 makes up for the marginally increased cost.

And on cars with active cam timing, you will see mileage and performance increases with higher octane fuel. They can usually retard timing to allow the car to be safely operated on lower octane fuel at the expense of some power and efficiency. Again, wether or not this is an acceptable compromise for you is a personal thing. It will undoubtedly be cheaper in the long run to use 87 octane fuel. The efficiency loses are more than made up for by the difference in cost. But are you willing to accept the slight reduction in performance for the slight increase in cost efficiency?

TLDR Summary:
- Ethanol will prematurely wear the fuel system seals on any car (not specifically designed to run high ethanol concentrations) produced before about 2003 or so, although not catastrophically. This effect will be more pronounced on any car made before the early 80's.
- At a similar octane level, E10 will display reduced performance and economy as compared to E0 fuel. This is usually offset by reduced cost.
- Most modern cars can compensate for and safely operate on lower octane fuels at the expense of reduced performance and efficency. These losses are usually small and offset by reduced fuel cost if you are OK with the small performance reduction.

 

So, why does my MY 99 XJR manual say 10% ethanol is fine? And why are my fuel injector seals hard as a rock? Atlanta GA has had ethanol by law for 15 + years.

 

I have been a resident of PA, NY, and VA with many road trips over the last several decades. E10 has been ubiquitous for far longer than 10 years, a lot longer virtually anywhere I've driven in the continental USA.

Brian

 

There is a video out there where a stock mid-90's Suburban was run on E85 for years, even though it was not marketed as such. They tore down the engine & it didn't look any worse off than a regular gas engine.