mikemareen

to 17.9 mpg from 19.7 mpg.

I got the timing belt, water pump, coolant flush, tranny flush, air filter, differential oil, spark plugs, and engine oil and oil filter change.

I dunno I'm thinking they put thicker 1040 engine oil, can that cause this change in mpg ?

I6turbo

iTrader: (1)

No on the oil switch.

Did you go with the OEM plugs? No goofy splitfire or other snake oil plugs, right?

How many "data points" do you have on the mileage change? One tank full could be due to lower quality fuel, different driving habits, or other
things.

The timing COULD possibly be off a tooth on one (or more) of the gears. Other than the questions above, that'd be the first thing I'd check.

cpcc

Probably the thicker oil

blacksc400

iTrader: (4)

thicker oil won't make that much difference.
Drive more and see.

alanchad

iTrader: (1)

Is it a major deal to check the timing possibly being off or no?

Thanks,

Alan

I6turbo

iTrader: (1)

I'm not sure -- I've never looked at the timing covers to see how much of a job it would be to get a peek at the gears at the points where the timing marks are. On some engines it's not much of a task, and on others it's a PITA. Sorry I can't help more...

junjdm

hmm....thats wierd......maybe more airflow in your clean filter there for slight power? reacting more w/ cleaner filter? more air coming in.....just a guess....

GS3Tek

iTrader: (8)

Was the fuel filter changed?

I'm not sure if I was smoking anything, but I swear on my old 95 corolla, when I changed that, the mileage did dropped noticeably and have wondered about it
oil change and driving habit were the same too-that's my uneducated guess.

DanozLS430

iTrader: (1)

Just a long shot thought.....The repair shop may have reduced your tire air pressure to 32-36psi on your 20's. I just increased mines to 45psi front and 43psi rears as of yesterday and the car is now rolling very nicely without the soft tire drag. I was getting 18mpg at 36psi on my 19's. Hopefully my mpg's will increase at the new setting.

Usuing the wrong grade of oil can reduce mpg by 1-2%.
http://www.fueleconomy.gov/feg/maintain.shtml

DanozLS430...

mikemareen

thanks dan, I checked the tire pressure and it looks like it's in the low 30's. I'll up to to 42 and see what happens

I6turbo

iTrader: (1)

As with much of the "information" found on the internet, that fueleconomy.gov info appears to be written by a political appointee who doesn't know what they are talking about. They probably read some marketing literature or some such as their source. LOL at the rediculously old source for the air filter information.

But re: the oil claim, a 10w30 oil will be essentially the same viscosity as a 5w30 oil once it warms up to operating temperature. It is not going to make 1-2% mileage difference (with the possible exception of that first 1 or 2 miles of driving).

DanozLS430

iTrader: (1)

I was getting 18mpg at 36psi all around after installing the new 19" tires. Firestone installed the tires and put in 36psi all around. I changed my fronts to 45psi and the rears to 43psi when cold. Now my mpgs' went up to 19.5-20mpg in 2 days on the same tank of gas. Got half tank left and want to see what the final results will be. My tires looks to be riding evenly at this setting for the front and rears according to the road marks on the treads.

DanozLS430...

GRAND_LS 4

iTrader: (2)

Not sure how long ago you had this tune up, but you should wait a bit as the car adjusts to your specific driving and shift points. That could make a difference as well.

big_blzr94

if you timing belt was installed one tooth off the engine light would be on for sure and the idle would be bad on the car.

mikemareen

ok guys I think I found the possible problem , looks like 3 tires were at 30 psi and one was at 18 psi.

I dunno wtf the mechanic was doing. ****!

everything is now set at 42 psi and it definitely feels lighter and floats easier. I see how the mpg calculations go.