I am running regular gas. I know... Thats a no no.. Can I switch it over to premium instantly and it not hurt anything. Also. Why am I getting such awful gas mileage. Is it due to just using regular gas?

 

Some cars can pull it off. Usually when it says premium REQUIRED instead of recommended, you need to use it though (the G).

 

The reason I didn't put premium in it is because previous owner was using regular, and I didn't want to switch it cold turkey and hurt it. Is this the reason my gas mileage is awful?

 

Probably lol. Merry Christmas change it out and track it for 3 fill ups.

I use Fuelly.

 

It is no big deal to switch gas. Lol infact there is normally no such thing as mid-grade; it's almost always mixed at the pump from regular and premium. You should notice a bit of a difference in throttle feel after about a tank. MPG probably won't be hugely affected, but you may see a bit of a bump. Sounds more like you need some maintenance done.

 

Your fuel usage is effected by great number of things. Just consider what manufacturers do now days to meet EPA standards. Toyota uses 0w20 oil to increase fuel economy, Chevy puts huge chin spoilers on trucks to make them more air dynamic and so on.

In your case you should be getting good 19-20 city and 21-25 highway. I get that with 220k miles on the 05 coupe.
To improve your millage start with cheap things and move on to more costly ones.
Gas is number one. Gs ECM can determine octane number of fuel and adjust fuel delivery based on the octane. Lower octane fuel= more of it being pumped into the cylinders as ECM demands.
So switch to Premium asap.
I can guarantee you that you will not get a major improvement after that switch since there are more factors that effect your millage.
Friction is the worst enemy of fuel economy so you got to look at every single component of the car that has friction.
Engine -Use good quality oil to reduce friction and increase it's efficiency.
Transmission............same thing.
Differential, also needs good synthetic oil to improve friction and increase gas millage.
Wheel bearings
Tire pressure
Spark plugs - need to be in good shape to effectively burn fuel so that ECM does not dump more into the cylinders to get the BAM that it wants.
Air filter- if dirty and not enough air gets in more fuel will be burned
Also if poor fuel was used it can with age wear out fuel injectors and as a result you'll be dumping more fuel into the engine than needed and out our exhaust.

So start with small, inexpensive things and move up the latter.

 

You are getting 12 MPG either because the way you are driving or short trips with frequent stops, starts and long periods of idling?

I never use premium and get excellent mileage with my current G37S and my previous 06 G35.

Four fill-ups from NJ to Florida, two fill-ups with short local trips while in Florida and four fill-ups on the return from Florida to NJ



Another round trip to Florida





IMHO using premium gasoline is a waste of money but is good for the oil companies and their stockholders.

My G37S has never seen a drop of premium.


Telcoman

 

Yo telco, dust that infotainment system!!!

 

I have been thinking about it, and I have a massive exhaust leak on the flex-pipe. I am thinking with that it is sending bad readings to the o2 sensors and its causing it to run real rich*

EDIT: meant to fix that *, I was in a hurry and am at work lol.

 

Lean = more efficient lol. Fix all maintenance issues first before trying to fix the gas mileage problem

 

wat?


^^this. Although your leak is after the sensors, so in theory it shouldn't effect it, but the sensors may be old anyways.

First things first, run premium gas. Technically the ECU has enough room to adjust for lesser rating fuels, but its better to not force it to make those adjustments as those adjustments are exaggerated. I'm assuming you just bought the car since you didn't want to make the fuel change when the previous owner ran regular? How many miles on the car?

Quick and easy typical maintenance things that could help:

Fix exhaust leak
Check plugs and make sure they are good and gapped properly. I'd be willing to bet they need replacing.
Check air filter
If your oil is old, change it and use recommended oil
Make sure tires are at proper pressure
Check e-brake tension (may be dragging)
Keep your foot out of the throttle

 

It only had 89,000 on it. Tires are at the right pressure and the ebrake isn't dragging at all.

 

Only 89k miles on a fourteen year old vehicle?

It must have sat unused for long periods of time. That is not good for a vehicle

Telcoman

 

Jesusssss with this guy ^^^
Yeah 6k miles a year avg
Cars prob worthless now because they didn't drive it enough
Give it up dude

 

That is almost 18 miles a day. If you aren't going but from work or to the grocery store thats not bad. It's fairly normal. Plus I have 50+ year old vehicles with less that 100k on them, still in superb condition.