A new engine was put in my car (5.5 gen) but before on the old one I was averaging 19.4 MPG and now its more like 17.6. When I was on my old engine, I had brand new spark plugs, pcv valve. Im not asking how to improve my MPG otherwise I would have done a search. Even when I drive in higher gears now, I cant get my MPG up there. I'll be driving on the highway around 60-65 in 6th gear and thats the only time it will reach 18.4 or so. As soon as Im local (keep in mind I still drive in higher gears when Im local), my MPG goes down to the mid 17's. And no, no abrupt stopping or anything of that nature. I even used Prestone fuel injector cleaner and it did nothing.

I would imagine that with a new engine, I would be getting better MPG or the same as previously if anything. Whats up with that?

 

Take it back to the dealer

 

I agree with Kevlo, take it back and demand they fix it now.

But seriously, with such a small drop in mileage (about 1.8 mpg) I would look at the things you did to the old engine that you haven't done to this one yet, such as plugs, filter, pcv, type of gas used, break in period, tire pressure, type of oil used. But even after looking at all that you may never match your old mileage numbers, or they may in fact get a little better.

 

what?!?!?!? less than 30 @ 65 MPH?!?!?!?!?!?!!
I get 30 @ 80 mph and it increases the slower I go.
Or do you mean avg with city driving? I can manage 17-18 shifting at redline from every stop.

 

give the engine to me....i will give you my engine that gets good MPG (but bad OPG)

 

I have always heard that a new engine gets lower MPG during the break in period. Should go up with time, but ask the dealer to make sure timing, fuel mixture is set correctly.

 

oh ok thanks everyone...it sucks b/c I spent hundreds on a major tune up on my old engine (plat spark plugs, pcv, etc) and its pretty much all gone now. I'll talk to the dealer tomorrow

 

mixed w/ city and highway driving

 

My thought was also break in!

 

Same here.

 

Its a very small diffrence.. 1.8mpg could have been caused by anything. give it a little time, let the engine break in just continue to use 93 octane. Also do the advanced timing, after i had it done on my car my milage went up slightly. Also didnt you have a intake on your old motor ? do you still have it on this one ?

 

How the hell do any of you guys get 30mpg? That would equate to well over 500 miles to the tank... I barely make it to 300 as it is and I never push it hard.

 

this is going to sound rather funny.... after doing my non fouler fix to get rid of my P0430... we just came upto PA for the long weekend... the car has averaged really good in the 3 fill ups so far.... 31.4 on the first... 29.8 on the second and 30.9 on the third.... and this is on a 2001 maxima gle -auto... with 142K miles... love it..!!

 

6th gear on the interstate. I don't soley go by the computer either. I drove from chicago to south of st. louis nonstop, did the math and still got 30 mpg as the result.

 

^^ So how many miles did you get on a full tank?

 

the computer isnt accurate at all. people cant use that alone to determine gas mileage.

 

couldn't tell ya, can't ever afford a full tank