Heh guys. I use 98 Octane fuel on my XJS. I just heard from a friend that 98 starts to go bad if you leave it sitting in your tank for more than 2 weeks.

I work away for 1 month at a time and just wanted to know if anybody knew if this was so?

 

Who knows how long the fuel sat at the refinery, distributor and gas station before you bought it? How many people don't use a full tank in a month, never mind two weeks?

Fuel is good for more than a year if kept in a closed container. Your friend listens to too many internet myths.

 

Yes fuel goes off, takes more than 2 weeks though.

If you lay the car up you can add fuel stabilizer, I used this in my boat when it was laid up for months.

 

Odd that you should post this question now Paul. A few us,and some in the know,mechanics etc,were discussing exactly this question.

We concluded that what some had said to prompt the discussion had led from the old leaded petrol (super as it was called) where if left for extended periods would be considered gone bad.
I have no problems and nor does the car/cars that have had 98 octane in them for over a year.
Even the fussy lawn mower that sits idle through winter runs just fine with the 1/2 tank that was left in it.

A month or few wouldn't concern me in the slightest.

 

If it goes bad in two weeks I'd have been in serious trouble a long time ago...my TR-6 and XJS will sit for a couple of months at a time some times...no trouble so far.

 

Cheers guys

Sounds like no problems at all for me.

 

no problems with fuel sitting for a couple weeks. but with newer ethanol fuels its best to top off before letting your vehicles sit as the ethanol tends to absorb moisture. but a couple weeks to a month wont hurt anything 4-6 months fuel might slightly degrade. but should still run fine. older fuel formulas used to store a lot better than current fuels though.

 

My 5 ltr mower fuel tin lasts me a year, never had a problem starting the mower or whipper snipper with it.
I recently started a chainsaw that had fuel well over 12 months old and it ran fine.

 

You guys have 98 Octane. The highest we have is 94 and thats hard to find.
98 is the crack-cocaine of fuel.

 

My XJ-S has sat for 8 months and I just emptied the tank into my C30... The fuel was neither off nor did it contain any water (the C30 is very sensitive to water in the fuel). So no problem what so ever

 

Not true. North America has a different rating system for octane from the rest of the world. Ours is rated according to AKI (anti knock index) theirs is rated by RON (research octane number). Rule of thumb is that RON will be 4 points higher than AKI, meaning that our 94 is 98 on their scale.

It's all irrelevant anyway as any modern Jag achieves full rated power on 91 AKI (95 RON) fuel. Paying for even higher octane is just wasted money.

 

Actually... Careful with that... My 89 catfree has a higher compression ratio (at least according to the papers I have). As it also produces more power than a standard cat'ed V12, it is recommended to use 98 ron. 95 ron is to be used only when a plug in the engine bay is altered so the engine knows what has been tanked.

Also, 95 ron here has 10% ethanol in it. I doubt a 25 year old XJ-S should be run on ethanol. My C30 gets that *****... But the Jag doesn't deserve using crap from the pumps... 98 ron has no ethanol in it (at least here in Europe!).

 

True enough- if the OEM specifies fuel higher than 95 RON then that overrides everything else. My comments were directed towards the N. Am. market where anything higher than 95 RON (91 AKI) is not commonly seen. I believe the cars sold here were tuned with this fact in mind. I was primarily addressing the misconception that high octane fuel makes engines produce more power as it contains more energy.

The Satan Ethanol debate is probably best left for another day. I've been using it for over 20 years, never had a moment's problem. Just about all gasoline here, including 91+ AKI has ethanol in it

 

I'm not saying ethanol is a bad thing... If my C30 would run on E85 I'd be running that all day. I just don't think it is a good idea to use it in a car, where more rubber was used, than a condom factory uses in a year!

 

Fuel lines that old are (over)due for replacement irrespective of the presence of ethanol. My other hobby is old Corvettes. We hear of one or two being lost each month due to a fire subsequent to the rupture of old cracked rubber fuel lines. To wit:

 

According to Bywater Jaguar standardized the lower (11.5 to 1) compression ratio *across the board* when Marelli ignition was introduced.

Do you have Lucas ignition?




No worries. My 1988 V12 ran sweet as a nut on E10.

Jaguar was OK with E10 even way back in the day. In fact the owner's handbook for my 1988 (Canadian) V12 VDP specifically mentions that E10 is OK to use.

Up in my neck o' the woods E10 has been standard issue for as long as I can remember...at least since the early/mid 90s. The way people talk you'd think the sides of the road would be strewn with dead and dying cars! I can assure you, that's not the case

If you *store* a car with E10 gasoline in the tank you might wanna take some precautions. If you simply want to *drive* a car with E10 gasoline in the tank, don't think twice about it.


Cheers
DD

 

Gasoline and rubber have always had a strained relationship. Same with gasoline and paper/cork gaskets, and all sorts of other things that were drying out and rotting to pieces wayyyyy before E10 was introduced.

I well remember being taught how to open up a Carter AFB 4-barrell carb to replace a dried-out accelerator pump.....in 1974 !

Nowadays people blame E10 if their girlfriend gets pregnant or trash cans get knocked over


Cheers
DD

 

Which is why my first (and current) task was to replace all fuel hoses and lines... Mine were all brittle... Couldn't take a V12 catching fire!

No I don't... I read about it being a cat-free "specialty". Until 1989, as 1990 was supposed to see the introduction of cats on all V12s as standard...

I guess yeah, you can do so, but my XJ-S is a "nice weather car" so I'll happily pay the extra few cents/liter for high octane

Sure, even modern cars still have issues with ethanol content in fuel. The mechanics are less often the problem. As I have an XJ-S with not totally known maintance history (was supposed to be with FSH but every service job I've seen was wrong or never done so...) I prefer to run on some common known fuels.

The first mass production car - the Model T - was built to run on ethanol... It worked then as it looks

 

You're confusing octane level with ethanol content. Two separate subjects. No direct correlation.

As Doug mentions, ethanol gets blamed for everything. Bona fide cases? Pretty rare.

 

I'm not confusing both... Last fuel I payed for was 98 ron (EU) with NO ethanol for a higher price than the next ethanol level (E5) with 95 ron (EU) or even cheaper (E10) with 95 ron (EU)

Though I must say, I did pay a lot more at shell for 103 ron (EU) with 0% ethanol