What is going on with my 2008 Passion?

[JamesWeatherford]

Hi Boys and Girls, I am seeing a marked decrease in mileage in my 2008 Passion. I purchased the car in June of last year, in the heat of the summer here in the Central Valley of California and I was getting right at 44 MPG, even with the A/C running full tilt, which I felt was pretty good.

I drive mostly conservatively, highway and city mostly. I filled up with premium a week ago and was surprised to find that I'm now getting 38 MPG! What is going on? Did the gas supplier change formulation, is there an additive to counter what they are doing, if they are. I also keep the tire pressure to proper levels too. When I ran my Cobra replica I added at a ratio of 5:1 Toluene to 91 Octane pump gas. You can purchase it at any paint store, Lowes, Home Depot. Would that help boost better mileage.

I wasn't concerned with fuel economy in a race car, naturally, the Toluene acted as a octane booster.

Anyway I am frustrated to see an 18% reduction in fuel economy, when I cannot see any obvious reason for it.

[Kermit]

Super stupid question since you're obviously a car guy. Is the air filter without a doubt clean?

[WhiteNBlack08]

How miles do you have on it? If you are getting close to 40K, it's probably time for plugs. I changed mine at the recommended 30K, but they still fine. I'm sure you should be able to go to 40K without any trouble.

I see you live in CA, did they recently change any rules regarding ethanol content? That could very significantly affect mileage.

[Kermit]

Good one on the plugs. That was my next question if the filter was clean.

[JamesWeatherford]

Kermit, I just had my 20,000 mile service and the air filters were changed, it could be plugs, I'll have that checked next.

In my assessment the car is running very strong, and fast when needed, but at the cost of fuel economy, which is to be expected if I had my foot down all the time I'd understand but I drive at posted speeds about 95% of the time.

California messes with the fuel formulas it allows to be sold, as a clean air measure, but it just messes with the tuning of our cars. Thanks for the heads up on the plugs WhiteandBlack.

Thanks guys.

[BB Benz]

You might want to check for brake heating to see if one or more are dragging against the drum or rotor. That could certainly drag down your mileage.

[wahi]

When you take out your plugs, check them for any indication of valve wear or improper detonation. Number your plugs so that you know which cyl they came from. Might tell you something. Good luck!

[Clava]

Be sure and check tire pressure, as a low tire can be a real mileage killer. I know you have a TPS but a simple check with a tire pressure gage will let you know if the TPS is doing a good job.
Just my 2 cents.....

[Kermit]

Originally Posted by JamesWeatherford

Kermit, I just had my 20,000 mile service and the air filters were changed, it could be plugs, I'll have that checked next.

In my assessment the car is running very strong, and fast when needed, but at the cost of fuel economy, which is to be expected if I had my foot down all the time I'd understand but I drive at posted speeds about 95% of the time.

California messes with the fuel formulas it allows to be sold, as a clean air measure, but it just messes with the tuning of our cars. Thanks for the heads up on the plugs WhiteandBlack.

Thanks guys.

My dad only has around 29k on his smart. At 24k I pulled the plugs to put new ones in and they were BADLY worn. It really needed a new set.

[JamesWeatherford]

I took a road trip on Monday from Lemoore to Sacramento on Highway 99, possibly the worst Highway in California BTW. 420 mile round trip, 10 gallons of premium gas = approx. 42 MPG which is pretty good all considered.

Before we left I checked oil, tire pressure, gave it a quick pass in the 5 minute car wash and away we went. I also picked up a air filter and put it in this morning, we will see if it helps the mileage. The old air filter was dirty!!!