which fuel grade - 93 or 89 or 87?

[anthonya9999]

This is my 3rd Volvo and I feel like I could run it on candlewax and not get knock in it.

When first out of school I drove an 81 Toyota Corolla -- the kind that still said "Use Unleaded Gas ONLY" under the gas gauge. You want to talk about knock!

I'd bet there isn't a driver in 1000 on the road today that would know what it is!

[LNB]

Our '04 XC 70 runs equally well on all three available octanes. We have switched to lower octane due to the cost and have seen no real mileage or performance differences. No knocking on lower octane gas either.

[dlr97]

I don't know if it can tell if the air pressure is lower and compensate for it to give the engine the same charge as at sea level.

Actually, a forced-induction piston engine can compensate for altitude to some extent (but not 100%). This is why turbo superchargers and direct-driven superchargers were used on piston-engine aircraft. Here is an interesting article from 1943(!) on the subject:
http://rwebs.net/avhistory/opsman/geturbo/geturbo.htm

In the old days, the pilot had to manually adjust fuel mixture with altitude, while modern engines have electronic adjustments using an absolute pressure sensor.

This is one reason I like the XC70 - no noticable loss of power when going from sea level up over high passes. I was pleased with the performance last week when we drove from the Sacramento Valley up to Lassen Peak to the 8000 foot level with a car full of people.

Dave

[john65b]

I am an engineer in a petroleum refinery, and we have knock engines in our lab... after every test cycle (10,000 hours, I think), we dismantle the knock engines, and the engines that run Un Leaded Regular ALWAYS have more gunk are residue than the knock engines that run Premium. Period. That reason alone is why I only use Premium in my 2001 XC. I am hoping it makes my new ETM last another 60k miles, but that's another story.

Now I also have a Jeep Cherokee that has a performance chip (HP boost of 15 - 20 HP) that requires I use Premium gas. The few times I spaced out and put ULR in, it knocked like a banchi.

I also see that I easly get 10% better gas mileage (chipped) with premium over ULR in my Jeep, which makes up for the 10% cost differential.

My 2 cents.

[KILOFINAL]

great post john65b. There must be a reason why Volvo recommends 91 octane. I have only put 91 octane in my XC since the day I bought it. I don't like paying $1.00 a litre, but that's the price I pay for driving this automobile.

[1Lieutenant]

If the manufacturer RECOMMENDS 91 Octane WHY would you use anything else?

Certainly they design in a safety factor for occasional need to use lower octane. It would improve their saleability to brag about the need to use only regular gas.

To cheap out and save 10-15 cents/ gallon seems very short sighted.

Steve

[1Lieutenant]

As a rough calculation, at 20 cents per gallon more for premium, I spend an extra $142.85/ year traveling 15K miles. This equates to $11.90/ month.

To me this is cheap insurance for the longevity of my vehicle. How many people read and disregard the advice given in the owner's manual and then complain about engine problems at 60, 70 or 80K?

Steve

[Raynald]

As a rough calculation, at 20 cents per gallon more for premium, I spend an extra $142.85/ year traveling 15K miles. This equates to $11.90/ month.

To me this is cheap insurance for the longevity of my vehicle. How many people read and disregard the advice given in the owner's manual and then complain about engine problems at 60, 70 or 80K?

Steve

I totally agree with you. As gas price increases (it's CAD$1.084/liter this week in my neck of the woods...), the dfference is even smaller in percentage since the gap between regular and premium have stayed about the same for quite a long time now. Regular is CAD$1.034/liter.

[miller02806]

I always use the highest octane gas. For one its a turbo, regardless of anything else. Second its an expensive car, so why gimp on the gas? Third Volvo recommends 91, so I go 93 to be on the safe side. Can't be too safe ya know.

[RedXC]

I've always use 87 octane in MY02. Sometimes I put 91 for the fun of it, but it doesnt really make much difference. For the gas prices, I thank Volvo for having the min is 87.