Just bought a 95 850 Turbo from Carmax with only 53k miles on her, and in immaculate condition. Everything is running well so far two weeks into owning it, and on my third tank of gas I've come to manage maybe 20-21mpg per tank(per the onboard computer) at best in 50/50 mixed driving. I just read a post with the 850R getting 25mpg driven hard. I'm getting no error codes from the car and it drives great, am i missing something....

 

I said I drove it hard for a while after putting in the sensor. I usually drive around 65 mph with some starting and stopping. I was getting 22.4 prior to replacing O2 sensor. I got the code saying the sensor was bad twice before replacing it. You may want to clean your throttle body. A car that old with only 53K on it might still have the original plugs. You might want to change them along with new wires and distributor cap. These are the obvious things. You probably should be getting better than 20-21, but these cars really vary. One guy is getting better than 30 in a 850 R. That's hard to believe.

 

As far as the plugs and distributor go, are they relatively straightforward to replace for the shadetree mechanic? On my last car, a jetta vr6, the plugs required a special tool just to pull them out and were built in to the wires and cost $$$. I don't mind spending $$$ for a good product though, are NGK still the best plugs and wiresets on the block? As for the O2 sensor, would it be wise to replace...or would that just be redundant being that I'm receiving no codes....For my first tank of gas I bought the most expensive Techron fuel additive I could find, i don't know if that was just placebo though....

 

I'm pretty much a "shadetree mechanic" myself and I was able to do the plugs, wires, cap and rotor pretty easily. I used all OEM parts. I think the plugs are Bosch, but I'm not certain. For the Turbo I think the plugs were around $30 for the set. I'm sure you can find directions on the internet on exactly how to do this work.

 

I would agree with Jim............a good tune up. I use Bosch platinum single electrode plugs gapped a tad wider than called for. I have had the throttle body cleaned and use Shell gasoline. I drive a 2.3 high pressure turbo and can reach 30 on the high way....the city mileage is around 20................so much stop and go and the air on all the time. Don't forget a new air cleaner....that also make an improvement.

 

I am new to the Volvo world. I have more experience in the Nissan and Mitsubishi world.

The rule of thumb that I have sort of followed -- Use NGK for Japanese cars and Use Bosch for European cars. For spark plug wires, I would use Bosch or Magnacore. For plugs, If car has turbo, I would use Bosch Copper. If car doesn't have turbo, I would use Bosch Platinum. There are rumors spread around the internet that the tips of Bosch Platinum-4's break off under higher than factory boost conditions.

But you are correct about NGK, I have NGK wires and plugs in my 1984 Maxima and 1985 Starion.

Regarding Distributor Cap and Rotor, you want to have copper or brass inserts. Avoid using aluminum. I have NAPA Echlin Cap and Rotor in my cars.
http://www.napaechlin.com/cpc3b.htm