OK so it is winter now... and with the high price of gas I thought that would try a tank of regular (87) fuel. I noticed the performance difference almost right away, but with poor traction and my soft winter tires on, I didn't think I needed the snap.

The wierd thing is that I appear to be getting better mileage. I don't think it is because I am driving less agressively... is it possible that with the ECU automatically detuning the engine the result is better mileage?

Normally with aggressive driving aand premium fuel I used to get 250Km (155m) to half a tank... I am now getting easily 300Km (188m). That's about a 20% improvement with cheaper fuel.

Is there any long term problem with running regular fuel?

 

okay I don't know if you experienced this after one tank of gas but if that's the case, you need to do it couple more times to make correct assumptionw hether regular fuel gets u better gas mileage. In actuality, better gas is believed to provide you with better mileage but i don't think that has actually been proved yet. So yeah, my bet is that you probably drove it less aggressively but not to a point where you notice much of difference in your driving style. Plus, on my worst day I get about 300 miles on full tank of gas and that's slightly more than 20mpg assuming I pump roughly around 14 gallons each time. For me, 3.2L, 260HP, 238 Torque and still gets 20MPG on my worst day puts smile on my face. Just my two cents

 

Reset your trip meter, fill your tank and log the mileage to check your MPG accurately.
Next time you need gas, fill it up again and divide.
Using the old “half a tank” method is highly inaccurate.

 

I agree with Shawn entirely, I once did a half tank measurement and got about 20mpg, but on a full tank I get no less than 26mpg. I drive like an old man.

Where in Canada are you from?

 

but shawn, with your method when do you determine that you used up all the gas that you just pumped?? For instance, say your gas light came on and you pumped roughly around 14 gallons. You reset your trip meter and drive till your gas light comes on and do your calculation? I just like to figure out my MPG by full tank of gas b/c more than likely I'll be pumping same amount of gas each time.

 

You don't care how much gas is in the tank, what you are doing by filling it is seeing how much gas it took you to drive "xxx" miles.. The key is to start with a completely full tank and reset one of your trip meters. Then when you need gas, fill the tank the same as you did before and devide that number into what is on the trip meter that you had reset on your previous fill. YMMV

 

Correct. I can't believe you have never done this before.

Say you reset your trip counter and drive 120 miles, and when you re-fill the tank, you added 6 gallons, you got 20 mpg. Do it again and see what you get. You don't have to empty the tank.

I had regular put in my car by mistake once. Car felt like shit. Even if the mileage was better, I'll never want to use regular.

 

I check my mileage every time I fill up. 24-27 mpg city and 33+ mpg on the highway trips! I can't believe so many people don't know how to do this. Oh, and I would never consider putting anything below 91 oct. fuel into my car. You don't save your self enough money to justify it.



Isn't gas getting cheaper everywhere? I only paid $2.21/gal for Prem. the other day. Seemed a hell of a lot better than $2.85!

 

 

 

Home is Edmonton, Alberta... no snow yet, but any day now.

OK... I agree that you cannot get a precise measurement of MPG with the half tank method, but I definately know if I am getting good mileage or shitty mileage. I occasionally monitor gas mileage on full tanks and do the math and it is definately correlated to distance travelled at half a tank. My best mileage on a highway trip (cruise set at 130Kph (80MPH)) was 29MPG (US gal) or 36 to the Canadian gallon.

I have had two full tanks through the car with regular gas and have got 600Km (375 miles) to the gas light coming on, with agressive driving (high RPM shifts and some WOT). Problem is that the roads are often slick now and without VSA I may not be able to drive the same way for another tank. The best way to actually tell is to go back to premium and see if the mileage changes.

I agree also with whoever said the car drives like shit with regular, though I might not put it that strongly. In summer I would never sacrifice performance for a couple of bucks on a tank. I didn't spend all that money on mods to neutralize the gains.

However, winter in Alberta is the great equalizer... on snow and ice there is no advantage in high output engines as you simply can't use it... you just spin.

The second consideration is that I am on rather pricey winter tires, and if I do hammer it , i will shread them because they are so soft. I had a stang want to race me the other day, and it pained me to give it a pass as I had my winter skins on. I think he would have taken me anyway... it sounder really mean. Judging from the sound of it, I would guess cam and headers. We can only hang with stock GTs... modded ones kill us.

 

Half a tank or full tank, it’s still VERY INACCURATE unless you’re tracking the miles using the trip meter and filling the tank TWICE.

 

PS…Off topic
My Subaru LOVES the cheap gas.
My dealer says don’t waste the money on anything higher then 87 octane because the engine was designed to run on the cheap stuff.
It’s hard to do after pumping exclusively premium gas for the last TWENTY years or so.

 

Hey Shawn... maybe I'm not getting it here.

I zero the trip meter every time I fill up. I also generally fill up at the same gas station and never top up after it clicks off... so the only source of inaccuracy is the personal judgement of when it is exactly half full. I don't have any problem doing this as the needle only stays exactly on the half mark for maybe 10 klicks (6 miles). I have has two CLs and both have been the same way. If I only get 220Km to a half tank compared to 300, then I know that relatively, my mileage is much worse. I do not know the exact figure, but unless a miracle happens in the last half tank, my mileage is going to be bad in the first case and good in the second.

I also don't get the "twice" thing. If you are suggesting checking for a repeatable result (not fluke mileage with a huge tailwind ) then that makes sense.

 

Why is this so difficult to understand?
It’s simple math, not rocket science.

Fill your tank
Reset the trip counter
Drive Drive Drive
When you’re down to a quarter tank or so, fill it up again.
Write down the gallons off the pump
Divide the miles you drove into the gallons of gas it took to fill up.
Instant accurate MPG number

 

Duh... I get that. This is grade 6 math.

What I don't understand is your comment:
"Half a tank or full tank, it’s still VERY INACCURATE unless you’re tracking the miles using the trip meter and filling the tank TWICE."

What do you mean by "TWICE"???

If you are not tracking the distance and fuel consumed how can anyone make any judgement about fuel economy?

My usual process is resetting your odometer on fill up (not filling up the neck sometimes and not others) and observing when the gas gauge hits the half way mark. This gives you an approximation of how good or bad you mileage is. It is not precise, but not everyone needs mileage computed to 2 decimal places. I have done the full tank calculation often enough to know that 300Km or more to a half tank is good... less than 250 is bad. I can understand that this may be a bit more tricky with miles than Km as you basically have larger units and therefore less resolution if you are using whole numbers. Still, a 30 mile spread (50Km) on half a tank is pretty obvious.

 

Fill your tank That's ONCE
Reset the trip counter
Drive Drive Drive
When you’re down to a quarter tank or so, fill it up again. That's TWICE
Write down the gallons off the pump
Divide the miles you drove into the gallons of gas it took to fill up.
Instant accurate MPG number

 

For ease... Use your cell, most of them have a calculator now. I use mine EVERY time I fill up before I drive away from the pump. Like Shawn says, you need to fill up at least twice and the more often you do it, the more accurate your MPG will be.



This is elementary school math....

 

my car has pulled a best of 41 mpg. it averages 33. 75% highway driving. i've never tried regular unleaded. the $.20 a gallon isn't worth it to me. even in my crappy cars i run 93 octane.

 

Your kidding right? 41MPG to the us gal = over 51MPG to the canadian gallon. My buddy who has a Civic doesn't even get that.

What were the conditions? all downhill? what speed were you driving? Was it on a full tank? Were you towed part of the way?

 

? #1) ...doubt it!
? #2) It's a high compression motor ~ stick w/the extra 2 or so bux per tank for the factory recommended 91 or higher.