Drove from west Michigan to St Cloud MN today. Temperature 75-80o F and a new set of Continentals with 38 psi. Good old 89 octane midrange gas.

Managed 411 miles to the first tank, which included going through a lot of stop&go construction traffic in Chicago and average speed of 70-75 when the road was clear. Computer said I had 75 miles left on the tank but it took 16.95 gallons. Computer also said I was getting 26.2 mpg but it calculatesto 24.2.

I then let my 15 year old daughter drive the next 120 miles at the speed limit of 65. The computer showed 29.2 mpg, which adjusting as above indicates I was getting around 26 mpg. PS - I did fill with 93 octane premium because the lower grades contained ethanol.

So, 24.2 mpgat 70-75 and 26 mpgat 65. But I don't have the patience to drive that slow.

 

Computer is always off by about 10%, Slower driving should give you better mileage. I put 114,000 miles on my 2.7t and it always did slightly better MPG using 87 octane. Better performance with Premium if and when you needed it as the timing stayed in it if you were into it hard enough to need the octane. That is some good mileage, is it a stick? I get better mileage now with my new 4.2 C6 chassis with 85 more HP. About 1.5 MPG better overall than the 2.7t did. Thats interesting as the window sticker is 1 less hwy than the 2.7t was. Things that make you go HHMMMMM.

 

MT6 is manual transmission, 6-speed. Car just turned 100k miles, so it's now broken in. I'm surprised that the 4.2l gets better mileage than the 2.7T - the 6 cylinder should be relatively efficient until you start hitting the turbos hard.

 

Ya, my automatic never got that type of mileage. I could never get over 23, ever!!! As for better mileage on my V8 over the V6, I know, that surprised the heck out of me too. The dealer let me take the C6 4.2 for a weekend and I could not believe the increase in mileage over the 2.7t. That right there completely sealed the deal for me. 85 more HP and an increase in MPG. If I run all highway the 4.2 will do 5-6 MPG better than the 2.7t easily. I figured they would be very close if you go by the window sticker. I don't get it. It is refreshing to get that kind of mileage with a luxury V8. Glad I didn't get the Infiniti. I really loved my 2.7t and thought I would get some buyers remorse. With 6000 miles now on the C6, none so far, I don't like worrying about door dings and scratches though. Didn't worry too much about it on a 114,000 mile car near as much.

 

Can I just ask a little question, I am a newb and I never liked the tires that came with my 2.7T so I got a set of Falken Ziex's, my question is why would you have the PSI on your tires all the way up to 38?
I dont know much about cars but my brother in law just looked at my tires one day and said holy sh*t those look to hard and they were at like 40, he said they should never go over 33/34. Is this BS or what?

 

Check the recommended tire pressure on the door sticker (mine is on the rear passenger wheel well). Mine recommends 35 f/r for a lightly loaded car with 17" wheels. I believe it goes up to 39/42 f/r if the car is fully loaded, but don't hold me to those numbers. My Conti's are rated to a max of 52 psi. I chose 38 psibecause I drive a lot of highway and was always told to add a couple pounds to reduce tire flex and heat buildup when driving a lot of highway. As a matter of fact, the day after I had the tires mounted I took off on a 630 mile trip from MI to MN.

 

A V-8 should get better gas mileage than a turbo V-6. Why? Gearing! The V-8 can be geared higher (lower RPM at a given speed) because it has the torque to move the metal at the lower RPM. The V-6 needs to be geared higher to achieve decent performance.

Bob

 

YA i checked my door also it mentions to put your front tires aroun 40+ if you have 1200+ pounds in the car, that is a lot of weight.
I always thought that you ge better handling with a little hotter tire and one that is a bit softer that way your car has less tendency to skid in corners etc...

Does anybody think the 4.2 gets better milage because it is a 6th generation so probably 5 yrs newer? From what I have learned is that having a 6th gear makes a huge difference

I have a corvette Z01 (C5) and it is a six speed manual, when I am on the highway doing 130km/hr and i hit cruise the computer says I am using about 6.4L per 100KM wich is about the same that a civic gets at around 90km/hr to 110km/hr. The sixth speed makes a huge difference.

 

If you are racing, I suppose a "softer" tire will put more tread on the road surface and not slide as much. That seems to make sense.

But extended highway driving on a soft tire causes a lot of tire flex which causes heat build-up. This can cause the tire to fail. Hence the recommendation to add 2-3 psi to reduce the flex. Of course, this is what I was told years ago, not recently, so maybe the newer tires are not affected. Maybe one of the forum members who is more of an expert on tires can chirp up.

It doesn't take a lot to get closeto 1200 lbs of weight. Four adult passengers = 600-800 lbs and a full trunk of luggage adds another 200-300 depending on what you carry. Clothes aren't heavy but cases of beer are!