Making Cars Lighter

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Hi Eric,

I have a 2005 Toyota Corolla CE and I just rolled over to 100,000 miles. I’m perfectly happy with the car and I’ve had no problems. I get regular oil changes and keep my tires overinflated. I am interested in getting better gas mileage as this past winter I’ve been averaging about 30 mpg. Over the summer I was getting about 35 mpg. I’ve read what you said about weight basically being the most important determinate of gas mileage, so I was wondering what you suggest if I want to make my car lighter without spending too much money.



  1. Thanks for these tips, every marginal improvement helps.

    If Mike at aerocivic is correct, we can all be getting 2 or 3 times the gas mileage our cars get in their stock condition. Either way, it reminds me of the amazing engineering feats of Daimler and his assistant/successor Maybach. Few of which we are incorporating or improving upon on a large scale lately.

  2. The difference in mileage is probably due to a couple of things. First, temps are cooler in the winter, so your car naturally burns more gasoline. Since fuel burns at a constant stochiometric ratio of 14.7 (usually), denser (cooler) air means more fuel burned. The second thing is that gasoline has been reformulated for the winter. That can also drive mileage down. Before investing in anything, wait till spring and see if your mileage returns to the 35 mpg. If you need a tune up, though, do it now and see if it improves things. The other suggestion of a K/N filter is a great idea. I have had them in my cars since 1990.

    I am thinking about doing a cold intake system to improve my car’s breathing. I’m not sure if it will help with the mileage, since I’m putting colder air in the engine, but the easier breathing may make up for more of the difference there.

    • I’ve seen minor but noticeable gains in fuel economy and performance/driveability (especially in winter) by using synthetic gear lube in manual transmissions and axles/transfer cases. I also like reusable high-flow filters such as the ones available from K&N.

      If you want to get a bit more involved, the next upgrade that usually pays the highest dividends is an aftermarket exhaust – or just mufflers. The OEM stuff is typically compromised by noise abatement concerns, cost and so on. Factory stuff is much, much better now than it was Back in the Day, especially the pipes themselves – but swapping in a high-performance aftermarket muffler(s) can often give you a nice bump up inpower and fuel economy, along with a distinctive exhaust note.

  3. I don’ think there is really anything you can do that will make a significant difference, in the weight department that is. However, making that unit breathe freely would help a lot and be a lot cheaper and easier to do. Free up the intake and exhaust. Do some research on good/cheap cold air intakes and filters. Check into a more free flowing exhaust. My $0.02.

    • In that, do you mean changing with a different air filter than I currently replace regularly?

      Also, what exactly can I do with the exhaust that could make a difference and how economical would that be?

      • Rough numbers here, but at 15,000 miles per year the difference between 30 and 35 mpg is roughly 75 gallons. Assuming $3.50/gal the difference is costing you $262.50 per year. An aftermarket exhaust system is going to cost at least twice, maybe triple that, and that’s before you get it installed. It’s also going to have a distinct boy-racer sound that you may or may not like, depending on your personal preference.

        See if you can find a K&N filter or some other kind of aftermarket air filter that breathes a little more freely. If I remember correctly these are reusable if you clean them. Other than that you’re likely to spend more on parts than you’ll recoup in mileage, especially if you aren’t planning on keeping the car another 100,000 miles.

        Feel free to call me all sorts of names if I got these numbers wrong; I don’t do numbers nearly as well as I do words.

        • Your numbers look correct to me, but if he can do it himself they’ll drop substantially. If you ain’t scared to help out at a shop I am positive they will let you wrench. I did my cold air intake and exhaust for the cost of a section of a 2.5′ x 3″ exhaust tube (custom intake), a $20 turbo muffler, $20 Pep Boys cone style air filter,$100 universal cat, and 8 or so feet of 2″ pipe (custom exhaust). Total cost was around $150. If you want to be more quiet you’ll need to spend a few more dollars on the muffler. If you are not mechanically inclined and don’t have the desire to try, it wont happen and the cost will out weigh the benefit.

      • I was thinking more along the lines of a cold air intake and a K&N, or similar filter element on the end. A more free flowing cat and muffler was also what I had in mind. I have a ’94 Saturn I did this on and it still gets 40mpg. About the same as my stock ’10 Yaris.

          • You are a complete fucking retard. I just filled up tonight and averaged 39mpg. Get over it, moron! Fucking Shit! One more moronic comment and I’m banning your entire net range of ip addresses.

      • Air filter changes do very very little to change gas mileage unless they are very dirty. A different exhaust will do almost nothing in a modern car. Those types of things made a lot more difference in the old carb days and there is a huge incentive for car companies to list the best miles per gallon possible so they already made some of the best changes possible. Ask any car expert and they will tell you the same. Reducing weight makes a little difference but I mean little. Reducing your car by 100 lbs is equivalent of dropping your speed by about 2 mph. Decreasing your speed makes a huge difference in gas mileage. Leave a minute early so you are not accelerating and braking all the time and it is possible you could save up to 20% on fuel usage.

        Winter driving does take more gas because a cold engine takes more gas to run.

        • “Reducing weight makes a little difference but I mean little.”


          Clover, again, what is your engineering/mechanical expertise? In your entire life have you ever successfully rebuilt anything with moving parts? (Not including your LEGO set, that is.)

          You’re an ass. A laughingstock.

          You make universal statements based on nothing more substantive than your feeeelings.

          Who the fuck are you to tell anyone here anything about anything?

          You have no relevant professional/experiential background to comment on mechanical/engineering questions, or vehicle design, or driving. All you are is a busybody. A louse. Not eve a maggot – because as Boothe and Brent observed, maggots perform a useful function.

          What do you do, other than post illiterate fulminations demanding that your will, your feelings, be imposed on others by force?

          So, fuck off. Take your government check and give yourself a prostate exam with it.

          • OK Eric, I will let you explain. Where is your information that replacing your air filter or exhaust in a modern car will improve your fuel mileage significantly? If you show me one bit of a fact on the subject I would appreciate it.

        • Clover, your latest fecal droppings were deleted – as will be future such droppings.

          I’m tired of dealing with you. Tired of responding to know-it-all posts written by an illiterate knows-nothing.

          You’ve had experts in various areas correct your blatherings and it doesn’t faze you at all. Most recently, Blake – who is an engineer who worked on air bag design – posted in great detail a reply to your earlier drivel, dismantling it patiently, item by item. Your response? Not, “oh. I see. I didn’t know that; thanks for educating me.” You just ignore what an expert, someone who knows what they are talking about, tells you. And let loose another ignorant fusillade of Cloverism.

          You pontificate about driving – yet haven’t got any background as a driver (other than possessing a state-issued DL, which isn’t saying much). You’ve got no real training. Never been on a test track or race track. Yet you feel no shame lecturing your betters who do have training and experience far beyond yours (nonexistent).

          You mouth off about “safety” and “the law” – but you have no expertise here, either.

          Just your own obnoxiously exalted view of yourself as the Great Law Giver and Arbiter of Everything.

          You see, Clover, it’s not that we disagree. I would welcome intelligent, informed, logical and rational disagreement. You may have noticed such on these boards. I (and the others here) engage such people civilly, and we have an intelligent back-and-forth.

          But with you, this is impossible. You are the grown-up equivalent of a screaming six-year-old who just wants what it wants. There is no reasoning with such a creature. All that’s possible is tuning out the noise.

          Which is what I intend to do from this point forward.


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