I normally dont do a lot of driving on the highway but have done a lot the last couple of days and I noticed that it runs at a really high RPM. Going about 70 to 80 on the highway it runs just under 3,000 RPM's this seems very high to me. At about 65 it will run at about 2,500 to 2,600 RPM's. What does everyone else's run at? I get horrible milage running like this. I was wondering if its not going into 4th or overdrive? I dont get good mileage in the city either. I was going to have my transmission flushed soon but dont think this will help much. Please let me know what your car runs at and what might be wrong?

Thanks

That's exactly what mine does so I think it's right. I get about 23-25 mpg on the highway.

:00000732: to the forum and let me help you out with a short Volvo Fuel economy lesson. One Volvo's are not known for getting great fuel economy.
Second your working with a 3500 pound car with a Cd of .36. that comes with a 3.73 rear end. Just to give you an idea how bad that is compare it to say a 850 and a S70 that have a Cd around .31 and the S60 and S80 both have a Cd of .28.
The 850/S70 gets through the air 14% better than your car. The S60 & S80 get through the air 22% better.
Your fuel economy is about normal for the 960/S90 2.9 24V I6. The RPMs are about right for MPH your running.
Remember one thing running 2500 RPM's or less gets you the best fuel mileage. Go over 2500 rpms and the gas mileage dumps. Now that we have covered the bad news.
There is good news you can boost the gas mileage by two to four mpg with a little work and expense.
First a little history on my 97 960 which is same car. When I got it about a year and half ago I got 25.3 mpg with the tires at the manufactures recommended tire pressure of 36 psi all around and the original life time transmission fluid. That was done running the posted speed limits on a trip which varied between 65-70 mph.
When I limited my speed to 65 mph the gas mileage jumped to 26.3 mpg.
I ran an Auto-Rx treatment through the engine to clean out any sludge from years of running Dino oil by the previous owner. I did a transmission service and flushed it. I filled it with Redline D4ATF synthetic fluid. I also went through the car and did a 30K service including changing the fuel filter. I also filled the engine with Mobil One after the Auto-Rx treatment and replaced the Power steering fluid with synthetic. Fuel mileage jumped to 27.4 miles per gallon at 65 mph. I raised the tire pressure to 40 psi all the way around and the fuel mileage jumped to 28.0 even. The second oil change after the Auto-Rx with Mobil One the mileage has increased to 28.8 mpg. This seems to be a normal effect with contaminates still being cleaned out of the engine.
Come Monday I'm making some changes involving the installation of a rear belly pan between the rear axle and the bumper. Two Volvo owners that have done it have seen Mileage increases of 1.5 to 2.0 mpg.
Here is a link showing the modification.Turbobricks