hvargas

Hi all:

Hoping for some input.

Purchased an '07 GS 350 AWD in June. For first few months the fuel economy was wonderful (about 10-10.5L/100KM or 23MPG). Suddenly, it seemed like overnight it went down to about 13L/100KM or 18MPG.

I noticed this big change when I received a 'Low Oil' warning on my dashboard about 5000KM into my first oil change (which was right after I purchased the car). I changed from conventional to synthetic and have since then read about the unfortunate burning oil issue.

Anyways, spark plugs were replaced by previous owner in December 2014. I've tried the STP fuel cleaner. New engine air filter. Tires are new and properly inflated. None of this made a difference.

Has anyone else had this drastic drop in fuel economy and been able to pinpoint the culprit? My driving habits haven't changed so I'm just looking for some advice on how to get those numbers back.

Side note, is there a way to reset the fuel economy to start from scratch? My next step will probably be to do manual measures to make sure the numbers are accurate.

Help!

ibidu1

iTrader: (1)

Maybe your gas stations switched to winter blend gasoline

hvargas

Hmmm nah sorry, I shouldve mentioned that it's been like this since August or September.

Does anyone know how to reset the trip information consumption information? I read somewhere to hold down the display button but that isn't doing anything.

monkeyRX

Did you switch on ECT/PWR mode on?

hvargas

I switch on and off depending on mood and if I'm traveling with family or not... but I've driven entirely on normal mode and entirely on PWR mode and it doesn't make a difference - still get poor fuel economy.

z2g2gs

Just a thought have you made sure the air filter element isn't dirty and clogged up?

haromania

I purchased an 07 AWD 350 today and a very large reason I fell in love with it at first drive is it had 28.7 saved on the MPG mode. He had just taken a trip in it and said it dropped from 30 even after driving around town a bit afterwards. I know that isn't what you want to be reading at the moment, but that's a pretty big discrepancy. Yikes, I hope there's a reason and you find it.

haromania

I bought an '07 AWD 350 today and fell in love with it at first drive anyway...but when I was looking over the MPG for that particular tank it had 28.7 saved from a road trip he just took. So that's quite a discrepancy, but in all honesty I am not 100% sure what their supposed to get. Yours does sound low though, I hope you find a reason for it and get that up a little bit. Gas won't be this cheap forever.

hvargas

Yeah, it was pretty dirty but I replaced it about a month ago and put in a K&N engine air filter. Didn't make a difference...

Can it simply be a matter of the engine getting older and not being as efficient as it was some years ago? Or is there usually a specific culprit?

UDel

Engines don't just suddenly lose power/get poor fuel economy as they age, with proper maintenance engines should still be making about the same power and getting the same fuel economy for a very long time and many miles.

Does the power seem like it has changed. Are you carrying more weight in the car?

Are you doing more stop and go driving or taking different routes then before?

When you received a low oil warning was your oil low or was it just time to change the oil. If it was low there could have been some oil burning issues, this engine is DI but it has regular fuel injection too but you may still want to look into carbon buildup/fouling as something may have gone wrong with your regular fuel injection. What about a transmission fluid change?

If that is not a problem and you can't get it diagnosed here is what i would try.

Use a better fuel injector/system cleaner like Redline or BG44K.
Clean the throttle body. DIY
Clean MAF sensor. DIY
Unplug battery, reset. DIY
Try a engine flush like Lubro Moly when doing your oil change.
Over inlfate tire a little especially for winter/cold temps because they will lose a few PSI.

hvargas

Power is the same and weight in the trunk/car is the same as well. Driving routes haven't changed either.

I should've clarified a bit more about the "Low Engine Oil Level" warning. It was about 5,000KM since I had changed oil (7,500KM interval). So I topped it off with about 1.5-2 litres of oil (pretty drastic) until the next oil change. The previous owner used conventional oil and changed it every 5,000KM so he never noticed a burning oil issue. Since I changed it to synthetic, it popped up for me and my mechanic simply told me it seems to be a pretty common issue with this engine.

Can burning oil contribute to poorer fuel economy or would that be a symptom of a another issue at hand?

Regarding transmission fluid change, I haven't done it myself and don't believe the previous owner did either but I'll double check. I thought that it wasn't necessary because it was sealed?

I'll read into your recommended DIY jobs a bit more and learn about those jobs. It's my first car under my name so I'm not yet the handiest under the hood.

Thanks!

Broncosi

Please keep this updated with what you find out! I have been consistently getting 17.5 MPG for the past 6 tanks of gas (since I bought my '07 GS350). So no sudden drop but I bought this car partly to get better mileage than my SUVs.

hvargas

Haven't really resolved it. I spoke with my mechanic and he pretty much said that it's probably due to the cooler weather.. and gave the example that his RX averages 11L/100KM in the summer and about 15L/100KM in the winter. Thing is that issue started before the temperature really dropped.

I've kind of just accepted how it is for now... I'll probably start investigating again in the new year.

Broncosi

I was prompted to post yesterday because I went to get some STP fuel system cleaner. I used it and filled up on a full tank from empty. I now get (according to the display)

hvargas

Sorry, what do you get? lol think you forgot the number.

I've tried STP complete and it didn't make any difference for me...