Toyota Nation Forum banner

1 - 5 of 5 Posts

·
Registered
Joined
·
46 Posts
Discussion Starter #1
I recently had to change the alternator on my Corolla and the belt was original and in bad need of changing as well, so I got a new one. Everything worked out well but now my gas mileage is reduced .7 mpg. It was getting up to 38.2 and now it's sitting at around 37.4-6. Now for the 3,000 miles I've had and been driving it it's been mostly highway miles at 50-55 mph, hence the higher end mpg. But when I first changed the alternator and belt I did the 10 minute idle relearn while in drive (because of course I disconnected the battery) and have been taking 1 hr long interstate trips a few times, along with that usual highway route.

I'm no longer driving the interstate and back to solely driving that highway route so I'm wondering does the car just need more time to get back up to previous average mpg, is the mpg lower because the newer serpentine belt affected it, OR have I tightened the belt too much? I tried adjusting it to about 1/4-1/3 in slack in the longest stretch of belt, as recommended from my research, but there's no way I see of accurately measuring that.

From trying to research this I've found lots of claims of reduced mpg after changing TIMING belts, but nothing about serpentine.

I'd be glad to hear any tips on the subject.
 

·
Registered
Joined
·
1,321 Posts
Are you manually calculating your mileage or getting a reading off the dashboard display? I found the factory display to have a lot of variance. I also think that if you don't reset it (which you did by disconnecting the battery) the reading you get is cumulative,not current data.
 

·
Diehard Rams Fan
Joined
·
20,330 Posts
That difference is small enough to be nothing. The last 3k miles has also been during the warmer months so A/C use would affect it also. There are so many factors that go into MPG. I don't think that is much to worry about.
 

·
Registered
Joined
·
46 Posts
Discussion Starter #4
Well it's going back up, currently sitting at a solid 37.7 (I have it set to average mpg) and I'm now reminded of how long it took to creep up to and finally break the 38 mpg barrier after I got it. I just had to go back to driving the usual route more. Guess I'm a little too OCD about that little number on the dash, can't help it. :rolleyes:

I have no doubt it will go back up now. My main concern was that I might have the belt too tight, but I really don't think I do and definitely don't want to loosen it back up more.
 

·
Registered
Joined
·
295 Posts
It probably was that 10 min. Idle relearn. After I did my head gasket I let it idle a good half hour while I was buttoning things up and it took a while to get the MPG average up.
 
1 - 5 of 5 Posts
Top