A few months ago I replaced my 89 240 wagon with a 97 850 T5 wagon. I was expecting to get a similar gas mileage with my 850 as I got with my 240, but it's actually a lot less. I used to get about 25 mpg in mixed city/highway driving on my 240, but I get a little under 20 mpg with my 850. Admittedly the 850 is an auto vs. a stick for the 240, but I am still disappointed with the mileage.

I have replaced the plugs, cap and rotor. There are no check engine lights. The engine gets up to temperature quickly and stays there so I think the t-stat is fine (although I will change that soon anyway).

I wondered if my O2 sensor might be going bad, but I think that would trigger a CEL?

Any thoughts on what else I could check?

Thanks
Rod

Posts on the RWD forum indicate a 5mpg drop from a stick to an automatic. It sounds like the mileage you're getting now may be close to your 240 if it had an auto. I'm getting 30 mpg in a '90 240 5-speed and 27-29 on the '98 V70 5-speed.

Things known to degrade mileage, all without throwing a CEL.

Vaccum leaks.
Aging O2 sensors.
Worn temp sensor.
Any spark plug except the Volvo 3 prong design.

Good luck.

Two more:

Using regular gas in a motor designed for premium.

Using no name gas instead of high quality brand name gas like Mobil, BP or Shell.

If you are using regular gasoline (87 octane), then that is the correct milage. Depending on driving style and air pressure in the tires, i get 20-21 around town and 26-28 on the highway with 90 octane.

Klaus
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Please answer, we need to know if the advice is good or bad. The 164 has a new home, all I am left with are 2 turbos :)

Wow, this is interesting. I use regular in my 854T, and I get 22.4 in mixed driving, 60% highway. I always thought is was a bit low, since I regulate the pedal respectfully. Now it sounds about right, since as I said I don't "hit it" often, and drive a pretty even speed.

Those knock sensors really work. Try the next grade up in octane for 2 tanks and I bet your computer will show an improvement. It should be cheaper than the extra 10cents per gallon cost.

Klaus
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Please answer, we need to know if the advice is good or bad. The 164 has a new home, all I am left with are 2 turbos :)

Thanks for that response Klaus, although i must say I am disappointed if that's the best mileage I'm going to get out the 850. I understand that the 850 has almost twice as much power as my old 240, but with technological advancements (the 240 engine is pretty much a 1960s design), I would have expected a similar gas mileage. I also have two Saab 9000 turbos with similar (actually better) performance than the 850, and they both get 25 mpg in mixed driving and close to 30 on long highway trips.

I guess it's that extra cylinder that does it...

I think you will need to drive downhill both ways with a tailwind to get close to 30 :D Yes, close to 30 is more like a 4 cyl turbo.