gulffishin

Oh, I forgot about the oil...

I had been changing it myself and using 5-30 synthetic blend GTX.

I think the dealer may have used a conventional 5-30, but i'm not 100% on that.

PFB

I am having a similar problem with my 2001 EE300. Over the last few months, I went from around 22mpg to around 16 mpg. No other issues, engine runs flawlessly. No Check engine lights, and no codes in Memory.

So today I called into a weekly radio talk show hosted by an extremely knowledgable, (almost un-stumpable) certified female mechanic, Explained my scenario, and after she asked me a few relevant questions, was advised that its most likely due to the hot weather over the last few months. Was told that some car computers over-compensate and this, combined with the AC being on almost 100% of the time will cause a drastic reduction in Fuel Economy.

She said that there is probably nothing wrong with the car, and that come cooler temperatures in September-October, that I will see my Fuel economy return back to normal.

So maybe your car is reacting the same as mine, and there is nothing wrong with either one of them. Especially considering that your problem also started in the summer time.

Phil

angmedic91

iTrader: (5)

^^^^^ Wow, very good information to know. Sort of makes sense as to why some people put in cold air intakes into their cars, cold air is supposely denser and has more oxygen molocules as opposed to hot air, less dense and less oxygen molocules. Any time the A/C is on, puts big demand on the engine.

Question, how much air pressure should a tire have? Does it depend on tire size? On the sidewall of tires, it just tells you max. pressure in regards to vehicle weight. So what is the best pressure to have for fuel ecomomy?

Thanks.

PFB

The ideal air pressure for a car's tires are those that are specified by the manufacturer. Usually found on the car's door sticker. A couple of Lbs. more will give you perhaps a bit (1%-2%) better fuel economy, but the downside is a harsher ride, and more suspension wear. More than 2 Lbs above the manufacturer's specifications will also cause the outer edge of the tire to wear out much faster than the centre of the tire. Anything less than specified and you stand a chance of ruining the Center tread or even ruining the tire.

I keep mine at 2 Lbs above the manufacturer's specs.

For accurate results, make sure that you measure the tire pressure when the car has not not been driven for at least 1 Hr. Also don't forget to check your spare.

Phil

gulffishin

That could be it... it makes since. I had the service done in May right as it started getting hot, and we've had a record hot summer this year-- it has been in the upper 90's with a heat index around 115 pretty much every day since then.
A little more $spent on gas is worth running the air IMHO

Lexmex

I checked out your tires, but none of the specs on your tire transition show much of any change, very slight, but nothing with regard to weight, 24 lbs, to even revolutions per minute..

The heat thing will come into play for sure. If you get MAF sensor or to a lesser extent a/f sensor errors and they come and go every so often, heat is at play there. We've had 90 degree weather (where it feels like 100+) for several months now here in Miami and it will definitely affect MPG even though I just replaced my a/f sensors a short time ago.

One other thing, and this affects me, is if the battery is on the way out, the charge/spark won't be as great and that will be affecting the combustion cycle. I've gotten the random misfire code on occasion after not starting the vehicle for a few days and the flashing CEL will come on for a few seconds and the go away. It is a P0300. In the RX300, we can tell the battery is going, because 1:00 a.m. will show up on the clock instead of the regular time, but even a check on the battery will show a low voltage. I've had my Optima Red Top 34/78 since Dec. 2004 and it has served me well, but just bought another battery given the problems I've been having. No doubt I am sure I will see improved combustion come the new battery, which is going to be a 21 lbs. Deka Big Crank ETX30L, over half the price of the Braille 21 lbs battery.

yeskay

PFB
it is other way around. low tire pressure will cause outerwear.

PFB

Oops, you are right. Thanks Yeskay for pointing it out. What was I thinking?

Phil

gulffishin

I reset the computer today, I guess I'll take it easy on the gas for a while and see if it helps and then wait for cool weather

RXGS

iTrader: (2)

PFB i will gurantee cold weather will cause a drop in mpg. If theres snow there is more firction on the road driving, as well as a winter mix of gasoline which contains more ethanol. At least this is what i have heard. With snow tires and this cold weather i have gone from 22-23 to 19ish which i figure is resonable although i hate getting below 20 even with all the city driving i do

miltonlin

A 20% drop is significant.

Have you checked under the hood and make sure the dealer put everything back in correctly - hoses and stuff. It's unlikely, but worth a shot. Once I checked and I got a free wrench :-)

Nberke

how do you know what your MPG is with out a computer doing the work.. On my 1999 ES300 i have no indicator telling me what my MPG's are

285exp

Please say you're being facetious.

miltonlin

Go fuel up your car slowly, but don't top off the tank.
Reset Trip inidicator to 0.
Drive until time to refuel.
Fuel up, preferable same pump, again slow flow, and don't top off. Variations in pump speed, topping, and if your car is on incline will skew your results + or -.
Record the gallons put into the car.
Take trip miles showing and divide by gallons.