FAST850R Posted March 30, 2012 Report Share Posted March 30, 2012 Hello, yes, its about bad mpg again. My car is 150k mile 1996 850R. Stage 0 was done 2 years ago. O2 sensor was replaced 1 year ago with OEM. I don't know why I am getting AVG 19 mpg 90% hwy 10% city with no WOT. Drive like a grandma, hwy average speed is 65~70mph. No Cel, no vacuum leak, no oil leak.... Where should I check? I am kind of lost here. I aldo got ARD orange tune to improve mpg, and I still get 19mpg. I checked spark plugs yesterday, and the gap was 0.032 so I closed the gap to around 0.026. I haven't driven car since because I have been busy. I am going to drive it this weekend to see what kind of mileage I will get, but I don't know adjusting the gap can imrpove MPG. I know tire pressure and alignment can affect mpg, and can they affect this much?? I know people are getting 25~27 mpg hwy. I barely get 19 here. Please give me lists to check. I really want to solve this problem. Thank you. Link to comment Share on other sites More sharing options...
atefitty Posted March 30, 2012 Report Share Posted March 30, 2012 Based on what you say in your post: 1. air filter, could be dirty in 2 years ya think? 2. A bad thermostat can kill gas mileage..Won't allow car to operate at correct temperature. Where does your temp guage sit?..Do you have good heat? 3. Coolant temp sensor is a main fuel control, a bad one can cause mileage to drop. 4. driving in sport mode 5. a lead foot 6. fat girlfriend Link to comment Share on other sites More sharing options...
Dick Dastardly Posted March 30, 2012 Report Share Posted March 30, 2012 Yes tire pressure can have a large effect. First thing I always check. It is free to check and fill so why not? Link to comment Share on other sites More sharing options...
850_GLT_owner Posted March 30, 2012 Report Share Posted March 30, 2012 It could be worse, you could get getting 16.5mpg, which is far and away the best overall mpg I've had in the 1.5 years I've owned the car. Thanks to this thread though I think I might look into the possibility of having a bad coolant temp sensor since my car stuttered and stalled after starting my still warm car last week when there were 80 degree temps outside. Good luck Link to comment Share on other sites More sharing options...
atefitty Posted March 30, 2012 Report Share Posted March 30, 2012 I've seen bad coolant temp sensors make the cooling fan run for 10 minutes after the car has shut off on S70's Link to comment Share on other sites More sharing options...
FAST850R Posted March 30, 2012 Author Report Share Posted March 30, 2012 Based on what you say in your post: 1. air filter, could be dirty in 2 years ya think? 2. A bad thermostat can kill gas mileage..Won't allow car to operate at correct temperature. Where does your temp guage sit?..Do you have good heat? 3. Coolant temp sensor is a main fuel control, a bad one can cause mileage to drop. 4. driving in sport mode 5. a lead foot 6. fat girlfriend Air filter was replaced with k&n filter 7month ago. I checked it and it looked very clean. Thermostat was replaced 1.5 years ago and temp gauge sits right at 9:00 o'clock position. How can I tell if I have a faulty coolant temp sensor? I do driving in sport mode but drive like a grandmother. The sport mode simply hold gear in high rpm, which is not the case for me. I barely hit 4 or 5000rpm. Like I said no lead foot here. Thank you for the advice. Yes tire pressure can have a large effect. First thing I always check. It is free to check and fill so why not? I usually check tire pressure and set them to 32front and 30 rear....the mpg is still low. I haven't checked it a while but when I set it to the correct psi, I still get only 20mpg. Can spark plugs gap cause bad mpg? Thank you Link to comment Share on other sites More sharing options...
Dick Dastardly Posted March 30, 2012 Report Share Posted March 30, 2012 Any brake calipers that are sticky? Link to comment Share on other sites More sharing options...
850T5M Posted March 30, 2012 Report Share Posted March 30, 2012 Any brake calipers that are sticky? I too have bad MPG, and wondering how I can check for a sticking caliper? When i changed my front pads, you normally have to push in the piston...the passenger side wouldnt go in, I had to force it in with a massive plier thing mechanism that puts like hundreds of lbs of force lol...the other side went right in with a channel lock plier. Could the passenger side be seized? To the OP, does the car role easily when on a slight hill, in neutral? Link to comment Share on other sites More sharing options...
FAST850R Posted March 30, 2012 Author Report Share Posted March 30, 2012 Hum.... I haven't checked the front caliper. I recently changed rear pads and those caliperss were fine. I don't rememmber whether my car rolls in N... Is there other way to check seized caliper? Thank you. Link to comment Share on other sites More sharing options...
Dick Dastardly Posted March 30, 2012 Report Share Posted March 30, 2012 Hum.... I haven't checked the front caliper. I recently changed rear pads and those caliperss were fine. I don't rememmber whether my car rolls in N... Is there other way to check seized caliper? Thank you. Jack up car in neutral and spin wheels by hand. Obviously if a wheel has a seized caliper you will know.. Apply brakes and repeat. Any resistance will present itself. Also in rear make sure the E-brake pads aren't hanging up either..they can de-laminate and cause problems (usually they make noise when thats the case) Link to comment Share on other sites More sharing options...
Keaton85 Posted March 30, 2012 Report Share Posted March 30, 2012 That tire pressure is low in my opinion. I run 36-40 depending on how crappy the gauge is at the gas station haha. Link to comment Share on other sites More sharing options...
BlackBrick Posted March 31, 2012 Report Share Posted March 31, 2012 yeah, i run about 36. Handles so much better, just feel holes in the road more. I get 17.8 mpg highway/city 50/50. But I have a manual boost control, so the turbo comes on much earlier. I generally get 1 mpg more in the summer. Link to comment Share on other sites More sharing options...
James A Sousa Posted March 31, 2012 Report Share Posted March 31, 2012 Are you using regular gas by any chance? How are you calculating mileage? I charge all my fuel and write my odometer reading on each slip. Once and a while I check 10 tankfuls or so. Last trip from Massachusetts to Minnesota to South Dakota to Minnesota and home with a full load of my daughter's stuff I got 28.5 - I get 23-24 around town. I have read that a K&N can ruin your air mass sensor. What was your mileage in the past? Link to comment Share on other sites More sharing options...
FAST850R Posted March 31, 2012 Author Report Share Posted March 31, 2012 Jack up car in neutral and spin wheels by hand. Obviously if a wheel has a seized caliper you will know.. Apply brakes and repeat. Any resistance will present itself. Also in rear make sure the E-brake pads aren't hanging up either..they can de-laminate and cause problems (usually they make noise when thats the case) Thank you for the tip. I'll check the calipers. I don't have any noises from Rear brakes, but I'll check them too. That tire pressure is low in my opinion. I run 36-40 depending on how crappy the gauge is at the gas station haha. The manual says 32psi front and 30psi rear. Do you run 36psi for front and rear? Can higher pressure improves mpg? Are you using regular gas by any chance? How are you calculating mileage? I charge all my fuel and write my odometer reading on each slip. Once and a while I check 10 tankfuls or so. Last trip from Massachusetts to Minnesota to South Dakota to Minnesota and home with a full load of my daughter's stuff I got 28.5 - I get 23-24 around town. I have read that a K&N can ruin your air mass sensor. What was your mileage in the past? I have been putting only premium gas since I have owned it. I drive it till I see the low fuel warning light, then I put 10 gallons of fuel. I drive it till I get the light again, and calculate it. The reason I install k&n filter was the bad mileage that I had with oem filter. I thought k&n filter would improve mpg, but I was wrong. If I can get that kin of mile from my baby, I will be very happy. Link to comment Share on other sites More sharing options...
aggarcia Posted March 31, 2012 Report Share Posted March 31, 2012 Something is really wrong for that type of mileage and your driving mostly city. I get 19/20 in town with stop and go traffic. Highway should be 24-28. As mentioned, I would check the coolant temp sensor. Plug in a scanner and see what the computer is reading. If bad the reading will be low meaning the car is running rich trying to warm up. Check for vacuum leaks and the fuel system is working correctly. Tire pressures and alignment also need to be checked. AG Link to comment Share on other sites More sharing options...
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