1997 Sentra Gas Mileage Boost Ideas...

Thinking about how to make my commuter car more gas efficient... I don't really use it for anything other than commuting so here are some ideas I had without going TOO extreme...

  1. Remove unnecessary parts that are heavy and lower mileage... Trunk rugs, unneeded tools, electric window motors(?), floor mats, hub caps, etc. Anything that is extra weight...

  1. Make sure my air filter is clean and free-flowing. Thought about a K&N high flow filter, but at almost .00, I don't think it will pay for itself in the long run... Especially with FI.

  2. Clean the throttle body on my car. At 160,000 miles, it's all messy inside.

  1. No jack rabbit starts or cruising overly fast. No heavy acceleration on the highway to pass, etc.

Any other thoughts? This is NOT a creature comfort car... I'm even considering removing the seats and hardware I don't use throughout the rest of the car...

Joe in Northern, NJ - V#8013-R

Currently Riding The "Mother Ship"

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Reply to
Joe
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Most of those things you're going to remove won't make much of a difference unless you get a couple hundred pounds out. Biggest bang will be a good front end alignment, tire pressure, engine in good tune, synthetic oil, slow starts, low speed, and highest gear as soon as possible. But if you do the math, it's probably not worth it.

Reply to
JimV

Like JimV said, you have to reduce weight significantly to see a mileage improvement.

Here's my suggestions:

Take out the spare tire if the occurence of flats in your commute is an extremely rare happening.

Keep your tires well inflated, the higher the better. I have a same car, a 98 sentra. Tire pressure should be 33 psi front and 29 rear. Maybe make it 34 front and 31 rear. Rolling resistance goes down and mileage goes up. Don't go too high, though, because braking ability goes down a bit as well due to the tires contact patch getting smaller.

Clean throttle body?? I seriously doubt that a dirty throttle body reducing mileage. It's not really blocking the incoming air. My beleif is that a dirty TB just reduces low rpm drivability; inconsistent idle, not so smooth down low, etc. It doesn't hurt, but doesn't really gain, either.

Make sure your fuel filter is only about 15K miles old. If it's older, change it. Spark plugs, change them at 25K miles instead of 30K miles.

Do you have bigger rims on your car? The smallest rims will get the best mileage, like the OEM 13s.

Operate the AC as minimally as possible. In winter, I only run it to clear the windows in humid, rainy weather. Otherwise, vent to get cold air.

CD

Reply to
codifus

Why do you think smaller rims will have any effect on mpg ? (aside from the fact that the costs of switching will easily outweigh any possible financial benefit from better mileage)

Reply to
still just me

It's all about the "contact patch". How much of the tire is actually on the road effect the rolling resistance. Small skinny tires will have a smaller contact patch than larger (and usually wider) ones.

It's true that it wouldn't pay to switch though.

Reply to
JimV

All the already posted ideas are good especially keeping the tires inflated properly. Tire pressure goes down about one psi for every 10 degrees drop in temperature so as cold weather approaches it is necessary to re-check the tire pressure. A big factor in gas mileage is keeping the slides on the disc brakes well lubricated and sliding freely. The tire should rotate easily by hand when the wheel is jacked up and off the ground. Good luck. Al

Reply to
al

It's more than that. Rotational mass. The heavy part of the wheel, the metal part, plays the most significant part in determining the rotational mass. Big 18" rims will have the metal part on the outer most part of the rim, with the lighter part, the rubber, being a very small part of the equation.

Here's another way to look at it; take the same exact car, one with 13" rims, the other with 16" rims. Brakes are the same, engine the same, everything else is the same, except the rims (and tires of course) Total width of the wheel is the same, though. The 16s have lower profile tires whereas the 13s have the higher profile tires.

The car with the bigger rims will be slower, and braking will be harder (longer) etc. All this is due to the bigger rims adding considerable rotational mass that weigh down on a car. This affects gas mieage, too. Considerably.

CD

Reply to
Codifus

FWIW, The same amount of tire is on the road, regardless of tire size. Simple physics. I will agree that a skinnier tire has a narrower contact patch, which might help.

I agree with the general premise, but I think you lose any gain when you make it practical in today's world.

Within reasonable limits (same wheel model, same tire model, same OD) the difference in weight between two wheel and tire combos that reasonably fit on a typical vehicle, say a 15" vs 16" wheel, will be roughly the same rotational weight at the same physical point.

If you start changing wheels, then maybe you can make a difference. We used to swap out larger wheel/tires for a pair of mini-lites at about

8 lbs each and that made a big difference. I don't think swapping one of today's ridiculously heavy 15" alloy wheels for a 14" of the same style will matter much - particularly when the additional rubber is factored in.
Reply to
still just me

Did you maintain the same OD but using a "+1" concept? Or was the performance difference possibly due to a change in tire diameter, or a change in contact patch allowing more or less wheel spin?

Interesting, but are there any back to back tests of the same car with different sized wheels? comparing difference years with a variety of factors involved is not a very scientific test.

Well, they _could_ go with 16" wheels, but the marketing department tends to make these decisions rather than the engineering department.

That's not why engines got larger. There's a marketing HP war going on.

Show me some back to back tests and I'll be happier. I'm not doubting that there is a definite possible effect here. I've seen it. I'm just doubting that you'll see much of a difference with the very heavy alloy wheels in use today.

Reply to
still just me

You can also go on a diet, ;)

Joe wrote:

Reply to
AS

I went from 175/70/13 to 175/65/14, so yes, the contact patch and overall diamater did not change.

True, it was an experiment amongst Maxima enthusiasts. Still, it was very enlightening.

Look at the 2000 Maxima SE. It had 16s. but the larger body absolutely dwarfed them. Even the 99 Maxima looks a wee bit wanting with 16s. The engineering department would have been in agreement with marketing because they knew the Maxima was only going to get bigger and weigh more. Bigger rims were inevitable to suuport the growing Maxima.

And a speed war with 0-60 times. The anniversary edition 2001 Maxima SE was being dragged down by its beautiful 17s.

If the alloys are heavy, then the effect is even worse. Alloy wheels are supposed to be lighter than their steel counterparts.

CD

Reply to
Codifus

Your contact patch did change shape. The size (sq in) of the contact patch doesn't change.

Two tires of the same rough OD in 16 & 17" sizes will have a very similar load rating, give or take 50lbs.

Again, I'd like to see some back to back numbers.

Supposed to be. Remember the phrase "mag wheels"? That came from the original wheels which were magnesium alloy. They were very light. Most "alloy" wheels today are very heavy. Typical weights are 18-24 lbs for popular import sizes. My mag-alloy wheels weighed in at about 8lbs. Today's 17" wheels are more about appearance than performance on most cars (with an unacceptable loss in ride quality and ability to handle real world pot holes).

Reply to
still just me

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