1997 850 Wagon NA Still getting crappy MPG

[dairyqueen814]

Unless the ambient temperature is UNDER 0 degrees Fahrenheit, the engine temp should stay between 183 - 220 (locked in at 3 o'clock). The air box thing you blocked only effects the intake air temp, not the coolant temperature. A cold motor runs rich, more fuel and could cause burnt valve issues.

You should get a engine code if you have vacuum problems.

Well I just replaced the thermostat (took like 10 minutes) the old one was seized up and the plate wouldn't move. Drove the car around and it got up to temp in 2 minutes and stayed there! I'll report back with mileage on my next fill up.
Thanks guys!
Nick

[rspi]

Hurrah!!! Solved that mystery. That is funny, that $18 part will save you hundreds of dollars per year.

For those that are watching...

[rspi]

As Rmmagow expressed, it is very important to do other "routine maintenance" things that will safeguard your ownership to help your car last for AS LONG AS YOU WANT TO OWN IT. These things include:

1. Heater core. One of the leading causes of blown motors.
2. Coolant hoses. If they blow, they will cause you to have a blown motor as well.
3. PCV system service/replacement. Can cause major oil leaks when ignored.
4. Timing belt replacement. Will destroy the motor if it fails.
5. Coolant fluid replacement. Helps keep the coolant system clean and running at a good temp.
6. Oil changes.
7. Fix any coolant leaks.
8. Odometer repair.
etc.

[dairyqueen814]

As Rmmagow expressed, it is very important to do other "routine maintenance" things that will safeguard your ownership to help your car last for AS LONG AS YOU WANT TO OWN IT. These things include:

1. Heater core. One of the leading causes of blown motors.
2. Coolant hoses. If they blow, they will cause you to have a blown motor as well.
3. PCV system service/replacement. Can cause major oil leaks when ignored.
4. Timing belt replacement. Will destroy the motor if it fails.
5. Coolant fluid replacement. Helps keep the coolant system clean and running at a good temp.
6. Oil changes.
7. Fix any coolant leaks.
8. Odometer repair.
etc.

Oh yes I'm well aware of the maintenance aspect of owning an old Volvo. I haven't checked the heater core but all my coolant hoses apear to be in good shape, I just did my PCV system, I have a timing belt job on the docket soon, I change my oile regularly, have no coolant leaks and I fixed my odometer when I got the car.

What goes bad about the heater core?

[erikv11]

Heater cores eventually fail and leak. It is not so common that you want to change one that isn't leaking, but it is something to watch for carefully. When a heater core fails it almost always leaks for a little while, gradually getting worse. There is plenty of time to catch the problem and fix it.

Keep an eye on the coolant level in the engine bay, if you ever see it start to drop then check under the floor mats for wet carpet. Or for the sweet smell of coolant in the dash vents.

[dairyqueen814]

I'll keep an eye on the heater core.
But I'm happy to report that after driving half a tank on the bad thermostat (about 20mpg) and the next 1/3 on the new thermostat.... I filled up this morning to 23.3mpg average!
Thanks for all the help guys!
I'm sure I'll be back..

Nick

[jacobharding]

I would consistently get 25-26 MPG in my 96 850 turbo. People will always tell you driving habits affect your MPG but I have tested this theory many times with several other vehicles as well and have never been able to get MPG's to change by any measurable amount. I have driven through full tanks as if I were driving Miss Daisy and other tanks like Steve Mcqueen on crack. The results always come in the same when I fill up. I have even been so precise as to face the vehicle in the same direction at the exact same fuel pump. Common sense tells you that it must make a difference but trust me it is not enough to be of any concern.

[rmmagow]

That's odd jacobharding, I found exactly the same thing trying to improve my mileage. ECO vs SPORT, driving like I had an egg between my foot and the loud pedal, keeping speed below or at 60 MPH. Yeah, a little difference but overall, nothing significant. The only real killer for me was bumper-to-bumper Boston traffic and even then 18~20 MPG most of the time. I lead-foot now, 100 miles a day, 24.4 MPG on mid-grade gas in a 98 LPT w AWD (disconnected).

[rspi]

@DairyQueen: Great info, that's about 16.5% better. Like saving 54 cents per gallon.

@ Jacob: Huh? What difference would parking in a direction make when fueling? A gallon is a gallon no matter where the car is parked. Driving habits can make a big difference, 15% easy.

[rspi]