1997 850 Premium Fuel

[davolvo]

With gas prices the way they are do I really have to put premium in my 1997 850 Base?

[erikv11]

I have always put 89 octane in my non-turbos. If a station only has 87 or 91 then I will go with the 91.

[polskamafia mjl]

Generally yes. The compression ratio in the N/A's approaches 11:1 and burned exhaust valves are a common problem caused by using low octane fuel.

[holmie_da_clown]

In the manual it says the car is designed to run on as low as 87 octane fuel but is optimized for 91 octane. Lower performance and fuel economy will come with the 87 but still at a cheaper price than 91. Personally I run 92 (no one sells 91 where I live) but if I needed to save money I wouldn't be worried about running 89 or 87 octane.

[northernlights]

A good measure of ultimate octane sensitivity is the cranking compression as that provides a metric with which to measure cylinder pressure.

The Volvo spec for a NA engine is 1.3-1.5 MPa. This equates to about 189-218 psi. An old school iron head engine needs 93 octane at the high end of that range, i.e. 210-220 psi, for optimum efficiency and power.

Aluminum heads help suppress detonation as they do not get as hot, but 218 psi is still quite high.

The 1997 manual states:

Volvo engines are designed for optimum performance on unleaded premium gasoline with an octane rating. AKI of 91, or above. AKI (ANTI KNOCK INDEX) is an average of the Research Octane Number, RON, and the Motor Octane Number, MON, (RON + MON/ 2).
The minimum octane requirement is AKI 87 (RON 91).

Assuming they are telling the truth with respect to 91 octane, then operating on 87 octane will require a substantial amount of spark retard under load to avoid detonation, but under light throttle cruising the octane requirements are much lower.

If you don't mind losing a little power, I'd give it a try and see if your fuel economy suffers. If it doesn't, then you are probably OK.

[MoVolvos]

_

I use to fill up with Costco Premium gas but now with the two older Hondas 02 CRV, 03 Odyssey and the 98 Volvo I've found all three like Chevron Premium the best. The cars run quieter, smoother, swifter, get better mileage and I am sure is running cleaner. My friend who was the original owner of the CRV always use the lowest grade said the CEL would be on for months on end and sometimes close to a year. He drove about 80 miles per day mostly freeway so he wanted to save money. Having owned the CRV for a year now it has only come on 3 times. Once I had to reset the other two times it went off by itself after some freeway driving instead of the usual 5 to 6 miles in town stuff. The CAT is original and being it is Canadian (KM) I think it is close to 200K now on that dying CAT.

Anyways, definitely run a name brand Premium (Costco is good mind you but). The extra mileage and cleaner running from the Chevron is definitely worth it, besides the higher MPG in most cases offsets the higher price not to mention the over all lower maintenance cost in the long run.

Blessings,

BKM
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[rspi]

I always run premium. It is no different than the 960 you had and I'm sure you were NOT running 91+ in that, were you?

I enjoy the car not running sluggish under load and I did get better mileage which offset the cost. So pumping lower octane will cause the car to get slightly lower gas mileage. Why strain the car and risk other issues while your not saving any money?

[davolvo]

Ok, I get it. I have putting in the middle gas and I fill it when it is at half; it doesn't seem as painful then. I wonder if the one and only owner put premium in it, if not could I project issues?

[rmmagow]

My V70 LPT has always had 89 (middle in New England) put in. I've tried 91 and 94 but for 40 cents more a gallon the 94 sure didn't feel any better or get better mileage. on the other hand, my wife also runs the 89 in her N/A S70 and said it did run better than with the 87.

[Kecy]

Hey, I use 98 octane in my 850 just about all the time , I get more mileage per/L on the 98 than I would get from 95, worth the few extra cts..