Easy Ways to Increase Your Gas Mileage

(We initially ran this article on increasing your gas mileage in November 2015. In light of recent events in the Southeast, we thought it might be a good time to bring it out again.)

Would you be willing to save money if you could do it without significantly changing your lifestyle or behavior? Spending less on energy costs is “easy money.”

While gas prices are relatively low compared to previous years, the US Energy Information Administration still lists the average household gas cost for 2015 at $1962. Adding 10% to your miles per gallon can add up, and makes an even bigger difference as gas prices rise. Even at current prices, a 10% increase in gas mileage can net you annual savings of almost $200. A 20% increase leads to almost $400.

Plus, increasing your gas mileage means fewer trips to the pump. That’s better for the environment.

Three culprits keeping you from getting your best gas mileage are tire pressure, “junk in the trunk” and driving style. Tweak those three inexpensive items and you can easily increase your fuel efficiency by 10%. Make a few more technical changes, and you may raise your gas mileage by 20%.

Easy MPG Tweaks for Non-Car People

Properly Inflate your Tires

Car manufacturers set a recommended tire pressure for cars based on a combination of factors: comfort, braking, handling cargo capacities, etc. Most tires have higher maximum tire pressure ratings than the car manufacturers’  “suggested” tire pressure.

The standard recommendation is “properly inflated” tires. I have been running my tires at the tire manufacturer’s maximum recommended level, though the government recommends to go with the car manufacturer rather than the tire manufacturer.

A representative from Michelin corporate once told me that “a lot of science and engineering went into determining the maximum tire pressure ratings for their tires.” He strongly suggested never running tires above those maximum ratings. That’s good  enough advice for me from the “Michelin Man.”

Conventional wisdom is that proper tire inflation means a 3% gas mileage gain over underinflated tires.

Junk in the Trunk

Here’s a gas mileage glutton that I need to work on:  I carry a bunch of things in my car that really need to go in my garage. Tools and materials from recent projects accumulate in the back of my mid-sized SUV. I currently carry hundreds of pounds of stuff that I need to clear out. Considering you lose 1% on gas mileage for every 100 pounds of extras you lug around, I may have lost 5% of my miles per gallon hauling unnecessary items.

I’m not alone. It’s easy to leave things in your car. Keeping a gym bag or a few extra toys in your car doesn’t make much of a difference. If the weight is significant, it’s a good idea to unload and store your items somewhere other than your car.

External storage can also reduce your fuel mileage, If you carry a roof storage bag you aren’t currently using, you are unnecessarily losing some serious gas mileage. A rooftop kit may only cost you 2-8% of your gas mileage in town. At highway speeds you can lose up to 25% of your gas mileage by reducing the aerodynamics on your car.  Rear mounted systems are more efficient (well, less inefficient) and only cost 1-2% in additional gas in the city and up to 5% highway.

Say No to Aggressive Driving

Fuel economy goes down 7% for every 5 MPH increase above 50 MPH.  Cruising down the highway at 80 is a pretty good way to ensure that you aren’t getting good gas mileage. If you want to maximize your miles per gallon, take your cues from the Sunday drivers, not the stunt drivers. Drive like Grandma.

I understand that 50 MPH may not be practical on an interstate. Much as I like a leisurely driving speed, even I have to jackrabbit up to 65 on I-40 just to stay safe in traffic.  I try to recognize that following the speed limit increases safety and saves a lot of money, and adjust my driving accordingly.

In town it also makes a lot of financial as well as safely sense to drive less aggressively. Gentle acceleration from stops can save another 5% in gas mileage.  Is a fast start from the stop light really going to get you to your destination faster? Or will it just increase the chance that you’ll bump fenders with the car in front of you and spend extra money?

Easy Ways to Increase Your Gas Mileage

MPG Tweaks that Require Some Automotive Knowledge

Proper Oil Viscosity

Conventional automotive wisdom has been to run heavy weight motor oils in older cars with lots of miles on the engines. My current vehicle has a recommendation of 5-30 weight motor oil. I have 158,500 miles on the car and like to run a 10-40 weight synthetic blend in the sauna that is a central NC summer.

In the winter, though, I mostly do short-trip driving, so I am going to switch to the manufacturer’s recommendation of 5-30 weight and go with a full synthetic. I plan to take advantage of a local part store special on the oil I need and a filter to do a winter oil change and see if I get any noticeable gains on the fuel mileage readout. The less viscous oil creates less drag on the engine parts, which is good for a few percent on gas mileage.

A Tune Up for Better MPG

Currently I am not getting quite the gas mileage I got when my SUV was new (at least new to me.)  On my last trip out of town, I noticed my gas mileage clocked in around 25.8 MPG. That was significantly down from earlier years, when I had gotten around 29.7 MPG driving 60 MPH in eastern NC. (I know, nobody drives 60 MPH anymore. Yeah, I’m that guy in the slow lane.)

My SUV still runs very well, but there are a few tweaks I’d like to make so see if I can get back to my previous numbers. I don’t think it needs any plug wires or changes to the computer controlled timing. With over 150,000 miles on the engine, it’s probably time for some new spark plugs.

I want to try the Bosch Platinum +4s, which are supposed to improve fuel economy.  If I  install a set, will I get any increase in mileage? (editor’s note: He did! See Replacing the Spark Plugs for Better Gas Mileage.)   Replacing the plugs will run around $24 for 6 plugs if I do the work myself.

I suppose the oxygen sensors may not be doing as good a job with over 150,000 miles.  My 2002 SUV has two oxygen sensors that are in front of the catalytic converters: one per side of the V-6 engine. The oxygen sensors measure the exhaust gas and adjust the air fuel ratio accordingly. As they age, they don’t effectively measure the exhaust gas as accurately.  That causes the fuel-air mixture to be more rich (using more gas).

It will cost me about $50 to replace the sensors, doing my own work.

There are new synthetic gear oils that are available and appropriate for use in differentials. Heavy weight or high viscosity gear oils have the consistency of molasses in cold weather.There should be some efficiency gains from switching to a lighter weight multi-viscosity synthetic gear oil for the differential in cold weather.

My SUV has a rear differential capacity of about 3 quarts. At about $10 per quart, this should cost about $30 or so for most DIY car folks. It can cost significantly more at a garage or lube shop to change out differential gear oil, though. This is probably not a high return on investment activity if you have to let a garage do it.

Just a Note

Many of the tweaks I’m going to try are much cheaper to implement if you can do them yourself.  When in doubt, leave it to professional mechanics. If you’re a rookie car do-it-yourselfer, getting some help from more experienced car enthusiasts may be necessary to do work efficiently.

If you don’t want to do the work yourself, a standard tuneup can run anywhere from $50-$200, but will increase the life of your car in addition to increasing gas mileage. And increasing the life of your car can save you even more money than tweaking your gas mileage.

Increasing Gas Mileage isn’t Complicated

I think the combination of all these suggestions should yield a mileage gain of 10% or more. My goal is 33 mpg highway. Hopefully, I don’t have to drive 50 MPH to achieve that goal.

Increasing your gas mileage doesn’t have to be difficult. Even if you avoid making changes to your car by changing your oil and tuning up the engine, you can see big gains in your gas mileage by keeping your tires inflated, not hauling around extra weight and  driving more conservatively. When you look for painless ways to save money, increasing your gas mileage with a few minor changes is a good way to start.

Jon has worked on cars as a hobby since he was a boy. His varied work history includes working as a professional mechanic for a national tune-up/lube company back in the mid ’80s. He still does most of his own maintenance and will talk cars for hours.

Do you think about maximizing your gas mileage as you travel? What tweaks do you make to get the best mileage possible?

Part of Frugal Friday on Aspired Living. and Annie and Everything.

21 thoughts on “Easy Ways to Increase Your Gas Mileage

  1. I know my husband is ALWAYS telling me to “drive like a grandma” in order to get better mileage! And he’s right; I have noticed a significant change for the better when I am more careful with starting and stopping, in particular. Thanks so much for linking up on Frugal Friday! 🙂
    Ann recently posted…5 Days of Frugal Stocking Stuffers: Day 3 = TeensMy Profile

    • The driving part is the hardest way for me to boost my gas mileage, even though it makes the biggest difference. Jon is much better about it.

  2. Thanks for reposting these actionable tips. They are a great reminder. My dad, ever the financial stickler, was always adamant about accelerating very gently. I’m glad to see some fuether support of the idea that aggressive driving costs you. Thanks again.

  3. Just heard on the news about the gas issues in the Southeast. We’ve been through our share of those issues over the last few years with the major hurricanes that came through the Northeast. Never fun. A great tip I hear to save money is to make sure you are using the proper grade gas for you car. Check your owners-manual. There’s no benefit to use a higher grade say premium (92 or 93 octane) if you car calls for regular (usually 87 octane).
    Brian @ Debt Discipline recently posted…Taking the Last Train to GloryMy Profile

  4. Hey, Jon. Thanks for the reminders. Bad on tire inflation. Good on minimizing excess cargo and driving style (I definitely drive like an old lady). And I never even considered the impact of spark plugs, oxygen sensors, and gear oils. True, gas prices are low (even accounting for the uptick in prices due to the pipeline issue), but it never hurts to make your car more fuel efficient. Great stuff.

  5. These are great tips for saving on gas, Jon. I’ve become a lot more aware of my driving since installing a telematics device from my auto insurer (which will get me a discount). While I was never a very aggressive driver before, I think twice before hitting the gas or getting too close to the car in front of me. Unfortunately I do have the “junk in my trunk” problem and nowhere else to store it. So the maintenance aspects (tire inflation, oil, and tune up) become a lot more important for me.
    Gary @ Super Saving Tips recently posted…Track Your Financial Health with These 6 Vital SignsMy Profile

    • Yes, I think you’re right, although newer cars are now making it easier to catch with tire pressure sensors (although some are more sensitive than others).

      I’d also look into having your tires filled with nitrogen. Often when you buy new tires, your mechanic can do this for a little extra, or may even throw it in for free. Nitrogen is more resilient to temperature changes than regular air- so you likely won’t have the pressure drop that typically comes when the seasons get colder. Nitrogen also doesn’t ‘bleed’ through rubber quite like oxygen. I wouldn’t say that nitrogen is worth the $30/tire that some tire shops like to charge, but if they’re willing to throw it in for less than $10 for all 4, I’d say go for it.

      • Hi Daniel,

        Have never used nitrogen in tires. Will have to do some research. We are members of BJ’s Wholesale Club, which also sells gasoline. They have the best “free” air! The air compressor has a “dial-in” air pressure, which automatically limits the tire pressure to the pressure you select. When we “gas-up” at a discount, we also check tire pressure with each fill-up. Have already noticed that pressure drop that comes with cold weather.

        Thanks for the comment,

        Jon J.

    • Hi Michael,

      Yeah, tire pressure is often neglected. Also the recommendation to drive slowly, accelerate slowly, and brake slowly. Most of the modern cars in our area seem to be properly maintained. However, you can smell the “unburned Hydrocarbons” in the air when you follow an old non-catalytic converter equipped car or truck! Grins!

      Thanks for the comment,

      Jon J.

    • Hi Laurie,

      That’s a good suggestion. We went to the coast of NC this weekend. The traffic in the slow lane was going 70+, so that limited my “slow speed” driving! We need more lanes, like a “really slow driver’s lane”! Grins!

      Thanks for the comment,

      Jon J.

    • Hi Jamie,

      Yeah, finally got the “Plugs Changed” in the SUV. They were the original plugs on a 14 year old SUV. Actually made it run alot better! Have almost 165,000 now, so will have to replace the Oxygen Sensors soon!

      Thanks for the comment,

      Jon J.

    • Hi Latoya,

      We have two “giant” stuffed animals in the back of Emily’s car, a Teddy Bear and a Dog.
      But I don’t think they weigh too much! Grins!

      Thanks for the comment,

      Jon J.

  6. I ALWAYS have nonsense in my truck loading my car down = worse mileage. Thanks for reminding me to clean it out to save a few cents at the tank!

    • Hi Katie,

      Yeah, I am the same way! Always end up with “hundreds of lbs. of tools” in the back of the SUV. Even had a “floor jack” in the back last week! Grins!

      Thanks for the comment,

      Jon J.

  7. I loved your suggestion to change the differential fluid frequently. If you are changing it out for season appropriate oil, that can ensure it’s being used most effectively like you mentioned. Since I don’t know what’s best for my car, I’m going to look in the owners manual to see what they suggest.

    • Hi Kendall,

      Planning to change out the current differential fluid soon. I believe it has about 70,000 miles and
      almost 8 years on it? Time flys on some of this auto maintenance. Originally, when I got my used SUV,
      the differential was making a little noise, so I checked it, and it was dry! So using an “old mechanic”
      solution, I used the 140 weight differential fluid until the noise went away. This was in the winter, so
      when I changed back to the regular weight differential fluid, I saw a 2 mpg increase in gas mileage!
      Want to try an even lighter weight differential fluid for this winter and see if it helps on the gas mileage.
      Have almost 165,000 miles on my SUV, and it gets very “light duty” here in the “flatland” of central NC.
      I would theorize that in even colder climates the viscosity of heavy weight differential fluids would tend to get
      very thick, and diminish the gas mileage. I’ll write about the winter differential fluid change “results” in the spring.

      Thanks for the comment,

      Jon J.

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