danyeru

Hey guys,

I have tried reading and searching through the site and can't find the info I am looking for.

I use Mobil One full synthetic and typically go around 7500 miles or so with a oil filter rated for 15,000 miles. I currently have 125k miles.

After every oil change I usually drop from 17 mpg to 15mpg... I have now been running 4 tanks of gas at 14-15 mpg... And it's frustrating me pretty bad.

Last few oil changes I noticed I am probably only draining out 4-4.5 quarts and not the 5.5 I put in.
Do you guys think using the high mileage Mobil one would help with the burning oil and the mpg issue?

In 7 years of driving this car, I have at best got 18.5 mpg and that was a rarity.. I know I drive a little hard and rev high a lot, but my 350z was driven the same way and I averaged 19-21 mpg. (Both have around same suggested mpg city and highway)

I typically drive 50/50 hwy / city Even when I drive 80/20 ratio I only get around 17ish... If I drive 100% hwy I can get 24-25mpg... But doing 90-95% hwy I will drop to 20ish..

Is this car just this terrible on mpg in general or do I have a bad engine or must this car be driven like my grandma drives in order to get decent mpg?

danyeru

If this is in wrong section please feel free to move.. I thought I was in 2nd gen

RyanV9

If you are using that much oil between changes, you should be checking your oil level more often to make sure it's topped up. I don't use Mobil 1 myself just because I've seen so many used oil analsys' that show it doesn't perform that well. It seems to shear down.

As far as your fuel economy, have you done general maintenance stuff? Filters, spark plugs and maybe O2 sensor(s)? That might help. Looking at fuelly it looks like you should average just over 20 MPG.

PIONEER

iTrader: (2)

at 7500 miles b/w changes, 1 1.5qt is ok. Generally at 3K miles, you should check and top off.

For the 14mpg
several things can be at play
cheap to expensive

Air Filter
PCV
Plugs
Wires
O2 sensor
Coils
MAF

How does the car accelerate?
Does it feel like it has good power?
Any black smoke when you accelerate?
Idle is smooth or does it stumble

jaymil31

So your first problem is the fully synthetic. You should not be using synthetics in the vvti motors from what lexus tells me. I use Valvoline for that last 7 years in my 2003 gs430. I may miss a half quarter of oil in 5000 mile oil change usually not. I have 200 thousand plus on the odometer. The first thing I would check is the maf sensor. They never seem to throw a code and they are usually going bad and if it goes your car either stops on just start acting up bad. If you search the 3rd generation gs you will find plenty of info on BAD MAF sensors with no code. Its cheap at autozone and I would recommend that for fuel issues. I change mine and got significant power and fuel mileage back. Check your battery this is usually another issue. Maf sensor are usually 60 to 80 bucks at auto zone and they carry the DENSO brand that the dealership uses.

danyeru

Thanks for responses guys.

What oil is recommended then for the gs300 with over 100k miles?

Is the MAF the sensor in the Air intake? I have used the MAF sensor cleaner on it multiple times over the years (once a year or so when it throws the code)

I do have an issue with starting off after coming to a stop... Lags bad, has even turned the car off before. I think I read in another post it was from the sensor being bad, or possibly needing to do a tranny flush. Is it safe to do a flush if one has never been done before and the car has 125k miles?

danyeru

Oh and can any moderator move this to 2nd gen please?

Thanks

danyeru

Pioneer,

- I have has the car for 80k miles... Have changed battery several times (Walmart highest model, which has corroded on me several times)
- Never changed plugs or wires. Read it's a complete PITA to change them in this car.
- Car accelerates awesome, except the issue with coming to a near full stop and car bogging down for a second... Once it gets over that bog / lag it's great in every gear.
- No black smoke that I or anyone I have asked has seen.
- the MAF gets dirty and throws a code once every 9 months or so... Have to clean it and code goes away... It slightly helped with lag issue for a while... It threw the code again for a day (didn't clean it, it just went away) and now the lag is back
- Idle was a tad rough at low rpms before I cleaned the MAF (that is the one in the air intake right). Runs fine for the most part now except every now and then when coming to a complete stop.

onelt1

iTrader: (1)

You might check your EGR as well. I was getting about 17 mpg on average with EGR and after removal i am getting around 21 mpg avg. Of course a bad EGR should throw a code. It is a pain to change the plugs and wires but you should do it anyways not only will you get better mpg your performance will go up. You might think about changing your oil a little sooner than 7500 miles. The oil will break down and start to turn into sludge around those miles. It may be full synthetic but I wouldn't trust any oil at that mileage, not even Valvoline, which is what I use. A lot of oils use paraffin as an ingredient to help keep everything coated, which is a wax.

danyeru

Is this what you mean? Or do you mean the part itself?

http://www.partsgeek.com/catalog/200...ve_gasket.html

danyeru

Can the EGR b cleaned using MAF sensor cleaner or does it need something stronger since its carbon build up? Throttle body cleaner?

Justin2JZ

2nd gen GS's dont have EGRs OP Seafoam it.

onelt1

iTrader: (1)

My bad I figured since it was the same motor it would have one, but I looked up some pictures and there isn't one.

danyeru

Yeah I looked and didn't see one...
Really hoping thisi is just the MAF....

Curious why are people against full Syn for the 2jzge?

Titten

Get new MAF, and find out if you really have to clean it. I've heard of Supra MAF's always going bad when cleaned. Yours might be different, but if it's not, cleaning it might have ruined it. So check that out. Do that maintenance items ASAP, as running at rich is likely being caused by those conditions and poor maintenance, and it's bound to ruin your cats. Also, make sure your tstat is doing its job and not running it in cold mode. Good luck.