Poor gas mileage 1997 S90

Lylos · Post by **Lylos** » 22 Oct 2018, 23:01

Hello all. I purchased a 1997 Volvo s90 a little over a year ago. The car has 110,000 miles on it and runs great. I drive the car mostly in the city averaging about 7 miles per trip, twice a day. I have been logging my gas mileage and the past couple tanks I have avgd about 14 mpg using premium gas. The highest mpg I've had is 19 mpg where most of the miles where logged kn the interstate. I will be checking spark plugs and I know the air filter is OK. When I purchased the car the parking brake line was stretched and I tightened it, perhaps this is sticking, is there an easy way to tell? Are there any other issues that could be causing such abysmal fuel consumption? Thanks!

93Regina · Post by **93Regina** » 25 Oct 2018, 19:06

Lylos wrote: ↑22 Oct 2018, 23:01Are there any other issues that could be causing such abysmal fuel consumption?

6-Cyl, 2.9 Liter...Automatic...3461 lbs.

OEM Tire Size ? "This sensor supplies the transmission control module (TCM) with an RPM signal. The TCM then compares the transmission RPM with the vehicle speed and calculates torque converter slippage. "

Post by **June** » 25 Oct 2018, 19:48

That number sounds about right. At 7 mile trips 14 mpg sounds right. 19 combined also sounds correct as well. Are you using 5W30? I drove a 960 for years and a 1998 S90 for a short time. Volvo cars were not made for gas mileage back then. According to the EPA your car should get 16 mpg city, 19 mpg mixed city/highway, and 24 highway on premium fuel. There is nothing wrong with your car. June

93Regina · Post by **93Regina** » 26 Oct 2018, 12:45

June wrote: ↑25 Oct 2018, 19:48sounds about right.

AW71L transmission can allow for good MPG if driver is trained, and city road conditions are favorable.

Below 45mph, it will coast (free wheel), like depressing the clutch in a manual. So, if traffic lights stops are avoided, and coasting is common practice, mpg will increase greatly. In bumper to bumper traffic, this will tick off other drivers when practiced, but one is gently slowing down to avoid stopping at next traffic light, and speeding up slowly to speed.
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Electronically controlled transmissions are a different animal. This article gives a good overview, but suffice to say if clutch slippage is greater than OEM specs, fuel economy will suffer.

An aggressive driver will never get good fuel economy....rapid accelerations, "keeping up with the idiots," and quick stops will decrease fuel economy.

As noted, a computer "calculates torque converter slippage," which is based upon tire size. An older torque converter may not have the same "grip" as a new one....as noted in article, "In conclusion, the type of friction that is used in a remanufactured torque converter is something that must be considered when choosing the correct unit for a specific application."

dm635 · Post by **dm635** » 01 Nov 2018, 07:12

It's been awhile since I've done a tank to tank run on the interstate. A previous 960 would get around 24 mpg all highway. Combined driving on my current 960 will not break 19 mpg. I have a check engine light which I believe is on of the oxygen sensors, transmission mode set to 'S' and I don't baby it. I don't abuse it either. But after out of 1st gear I regularly take it to 4-5K rpm"s. Love this engine. I'm away from city driving so it's not stop and go. Every fill up I'm always in the 19's. 202K on engine.