I just commented on everyone's favorite topic: Motor Oil, but have found that comments on fuel preferences to be few and far between.

The other day, I was nearing the end of a long drive (over 100 miles). It was raining and I was tired and, low on fuel, had to hunt for a gas station. I found one and seeing it was cheap at $3.35 a gallon, punchily filled half the tank before realizing I was using 87 Octane - Lo Test.

High test at this station was about 5 bucks a gallon, a dollar more than I usually spend, but upon waking up, stopped the flow of Lo and filled it up with Hi-Test. Car seemed to run fine the rest of the way.

But I got to thinking. Most cars can compensate for lower octane, though with reduced power. Will a '97 Jaguar XK8 tolerate lower octane fuels without damage? I wouldn't do it in the heat of the summer, but the weather here has been unseasonably cool. And I seldom drive the car hard, perhaps with the exception of a spirited stab of throttle on the acceleration ramp.

What say you fellows and ladies? Can I (we) get away with Lo-test fuel?

 

In the UK I use E10 bog standard fuel in my XKR. I've used premium before and didn't notice any difference at all, besides the extra ethanol should go to some lengths to help cool combustion. My fuel economy didn't change so I just feed it bog standard cheap fuel because it will go through it quickly anyway.

 

UK ordinary E10 fuel is RON 95. That's quite a bit more than USA (AKI?) 87.

I guess (!) the car will be OK on some 87, at least occasionally.

 

Other’s more knowledgeable please
correct me, but I believe the knock sensors will retard the timing of there is an low octane issue severe enough to cause knocking, thus mitigating any possible damage.


That said, the car will not produce identical power with lower octane fuel, whether the knock sensors are activated or not. That is the major drawback to using lower octane fuel. The potential energy release is just not there vs using premium fuel (when the engine in question is designed to utilize premium fuel).



Z

 

Knock sensors always active advancing the ignition until it knocks and then retarding ..cycle repeats to keep it just shy of knock.. thats there function.

Handbook says min 91 octaine

 

Yes - but maybe a fuel below minimum spec might be out of the adjustment range? (Why risk it!)

Yes.

Just to confuse (?) some... in the UK "Premium" is beyond what the car needs. Our non-premium (RON 95) is OK.

(Premium here is 97 / 98 / 99 / ...)

 

Thanks everyone for their input.

I think Jag V8 said it best in "Why risk it?"

So with my go-to gas station only charging 50 to 75 cents more for premium, I'll continue. And will try to make sure to fill up before a long trek.

But when the station charges 2 bucks more per gallon for the powerful dino-juice, I'm inclined to risk it ! Especially on cooler days when I only need a part fill. Two bucks can add up to a lot of dollars!

 

There's no way I would risk that low octane gas. As you only added a small amount, no harm done. Definitely worth the extra for the good stuff.

In the UK, regular 95 octane (e10) is equivalent to $8.60. We pay even more for 97 (e5)
I have started using the 97, as I don't want the increased ethanol content fuel, which is bad for older type plastics and increases condensation in the tank.

 

According to a 2012 article in the Economist, UK 97 Octane is roughly equivalent to 91 Octane gas in the US - usually called mid-range. I'm not convinced this is 100% correct, unless you have a Super-Duper blend!

https://www.economist.com/babbage/20...-needs-premium

However, the article goes on to suggest that it's probably wise to use the hi-test stuff in a car where the maker recommends it, because there is really no telling if the lower octane damages the engine or not.

By the way, we in the US can't easily escape from ethanol flavored gas. I once looked and found the only non-ethanol gas available in Maryland, where I live, is at airports. And then it's likely to be leaded, which is harmful to both the car and owner. In fact, some stations sell E15, though I have yet to see it. As far as I know, we don't have an E5.

Gas prices in the UK, it seems, are about double the US price. So I suppose I should quit whining. Though to be fair, you probably don't have to travel 100 miles round trip to visit your friends and family in the UK.

 

89 or mix up some 90 and you won’t have problems