Figured after 100k miles is was time to swap out the old fuel filter for a new Mann filter. Had the shop install it same time they changed out my tranny fluid. Problem is, before the new filter my last 3 fill ups were getting me 24mpg. Now after the new filter my gas mileage has dropped to 21.7mpg over the last 3 fill ups. Is there a break in period? Or is there something else wrong?

My driving habits have not changed not has my commute.

 

It makes sense that a new filter would flow slightly better than an old dirty one, right?
Besides the little bit of gas in the old filter, did they lose a little when they changed it out? You'd have to factor that in. And maybe they took it out for a "Spirited" test drive afterward.

 

He said "over the last 3 fillups" so I don't see spillage or test driving having any bearing.
I changed mine out at 45k and noticed NO difference, was 28 before and 28 after.
( I do mostly all highway driving )

It probably wouldn't hurt to drive it for 10-20 minutes, then pull the plastic cover off and see if maybe they didn't tighten up one of the connections. ( That could get REALLY expensive if it gets on the exhaust and a rock chip or something causes a spark !!! )

 

Yeah, if there was any spillage, it wouldn't factor into my last fillip since I had it done 2 fill ups ago.

Not sure about the connector, I know they used brand new clamps to secure the hoses, but I'll double check for any leakage or loose fittings. Surely though if there was I would've smelled some gas after driving, especially since I park it in the garage.

And no, they didn't take it for a spirited test drive. I was there the whole time, lol.

 

I took that to mean that he averages every 3 fillups. So, any loss from the first tank would have bearing on all 3 tanks, yes? My car is tuned to use as much fuel as possible, LOL.

 

My first fill up after the fuel filter was 21.5mpg. The last fill up before was 24.5mpg. I lost 3mpg

 

Apart from fuel leakage I can see no logic for this at all.
Is your average gas usage calculated over all previous fills or just the last three?

 

A new filter should not make a difference on most cars. But on the Crossfire, the pressure regulator is built into the filter. If the pressure is not as high as the original one, the fuel may not spray efficient from the injector like it should causing lower fuel mileage. Just something to think about.

Maybe you need to check your fuel pressure and see where it is with the new fuel filter.

James

 

Your sig. says you get 22.9 avg. mpg.

 

Since we're all guessing here.. lol.
Regulator.. pre filter or post filter? If its pre filter I could see a drop in pressure to the injectors, and would think injector timing would compensate for a/f ratio. Possible car is still compensating and slowly adjusting?
Thoughts of relearn required come to mind.. like disconnect battery for 20 minutes or so?
Just speculations..

 

Click on the fuelly link in my sig. It'll show my gas mileage for the past 6,000 miles.

 

The OP has not mentioned adverse affects on performance which I would suspect would be noticeable. Straight from the box a Mann filter should be golden, These are probably all inspected before shipping, I suspect maths errors.

 

So? .......
You are worrying about nothing.

 

Kinda what I was thinking. low of 21.5, high of 24.5, avg. 22.9 (o.k.,23)

 

This is the 1st car I have ever owned that would get above 20 mpg.... I am happy...lol I also think it would out run most of the other cars I have owned...

 

Some of you need to enjoy your cars a little more, damn near 30MPG is not enjoying a performance car at all

Should have gotten a hybrid LOL

 

Bah! The only hybrid that comes in a stick is the CR-Z, and I'll be damned if I'm lugged to an anchor that does 0-60 in 9.6 sec.

 

Bingo! Hybrid, micro car, whatever. If it is a great concern for the reason of needing to (commute, only car) buy a really cheap older, efficient car for this. My Crossfire will stay parked and I'll ride a bike before I'll expose it to the fools that...grumble, grumble....

 

Update:

Guess the ECU finally compensated for the cleaner fuel filter, filled up today and got 29mpg. You read that right, mostly highway and I'm back to being a happy camper

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Damm, wish fuel was that cheap over here - paying almost $10 a gallon