Something for nothing?

[Trongersoll]

Hi, I'm new here. There is something that i've been contemplating but I'm not sure of the results.

Ok, i'm thinking of getting a 2001-2 Camaro or Firebird. Oddly, or not so oddly depending on your perspective, Gas mileage is a consideration. The V6 is rated at 28-29 MPG Highway. The V8 is rated 23-26 MPG depending on the transmission.

Ok, so far so good. now for the science part. The stock tire is p235/55R16. If I replaced the rear wheel & tire with a 235/65R17, according to www.miata.net/garage/tirecalc.html if your rear axle is turning at a rate where you would be going 60 mph with the stock wheel/tire you would be going 66.5 MPH.

All things being equal, this would be an improvement in Miles per Gallon as well. Sure performance would take a hit in acceleration, but not everyone worries about 0-60 or quarter mile times. It is my understanding that the average car only needs about 35 HP to do 55-60 MPH. This is why newer V8s shut off cylinders on the highway. So, i suspect that either engine is producing wasted power.

The V6 puts out 200 HP, the V8 310 HP. Now my question is, yes there is a question here. Would the larger wheel & tire combination actually see a real MPG improvement or would it require more gas to turn engine at a given RPM due to the loss of a bit of mechanical advantage.

oh, and yes i know changing the gear ratio in the rear end could accomplish a similar result, but tires are easier to change.

[Trongersoll]

I asked this Question on Yahoo Answers since i didn't get an answer here. The concensus was that, with a light foot, yes there would be an improvement in MPGs. Oddly, I've found that just about any performance mod made to a car will, with a light foot, result in improved gas mileage. I find this odd.

There is a claim that improving airflow will improve MPGs. Add a low resistance air filter, headers, performance Cat. and muffler and resist stomping on the pedal and MPGs will go up.

OBDII reprogrammers claim to offer an economy setting. I'm not sure what they are changing, maybe leaning out the engine a bit?

I'm not concerned with whether the savings would warrant the cost. I just feel it would be cool to have a 35 MPG Camaro. Something that could comfortably burn up highway miles with out requiring a second mortgage.

[tskeeter]

You missed it. Rick actually did answer your question back on July 2nd.

You asrent going to see enough of a gas mileage difference to cover the cost of the wheels and tires.

I believe that Rick is absolutely correct. Minor, if any, improvement in gas mileage. Adverse impact on drivability (acceleration, hill climbing, head winds). What you would increase is your probability of getting speeding tickets, as the larger tires would cause the speedometer to show a lower speed than you are actually going.

Actually, in terms of gas mileage, I think you could get more out of using a light foot, keeping your speed down (it takes 4 times as much energy (gas) to overcome the wind resistance at 80 as it does at 40), keeping excess junk (read weight) out of the car, keeping your tire pressure up to where it belongs, not driving around with a ski rack or bike rack you are not using at the moment on the car, etc. And, in true YM style, all of these things can be done for free!!!

Keeping your speed down will have the biggest impact. Our 2000 minivan with a V6 would give 23+ mpg on the highway at 70 MPH. At 80 to 85, the mpg dropped to 18, a 22% reduction in gas mileage.

[Trongersoll]

Jul 22, 2011 20:23:03 GMT -5 @rj said:

Jul 22, 2011 18:31:33 GMT -5 tskeeter said:

You missed it. Rick actually did answer your question back on July 2nd.



I believe that Rick is absolutely correct. Minor, if any, improvement in gas mileage. Adverse impact on drivability (acceleration, hill climbing, head winds). What you would increase is your probability of getting speeding tickets, as the larger tires would cause the speedometer to show a lower speed than you are actually going.

Actually, in terms of gas mileage, I think you could get more out of using a light foot, keeping your speed down (it takes 4 times as much energy (gas) to overcome the wind resistance at 80 as it does at 40), keeping excess junk (read weight) out of the car, keeping your tire pressure up to where it belongs, not driving around with a ski rack or bike rack you are not using at the moment on the car, etc. And, in true YM style, all of these things can be done for free!!!

Keeping your speed down will have the biggest impact. Our 2000 minivan with a V6 would give 23+ mpg on the highway at 70 MPH. At 80 to 85, the mpg dropped to 18, a 22% reduction in gas mileage.

actually, if you read the question, no where does it ask about savings vs. cost. The question was whether or not the engine produced sufficient surplus power to power the loss of mechanical advantage due to the larger tires without consuming more gasoline.

[tskeeter]

actually, if you read the question, no where does it ask about savings vs. cost

Sorry about that. When you post on a money/finance board, title a post "something for nothing", and indicate that "gas mileage is a consideration", you're probably going to be burdened with unsolicited opinions about the financial wisdom of the options you present.

So, upon further consideration; putting bigger tires/wheels on your car is still not a cost effective way to improve gas mileage.