El Codo's Bag of Tricks for Getting the Best Gas Mileage

'87 Dodge van parked in palm grove.

Miss Lousiane

editor’s note:  We don’t call him “El Codo” for nothing. Some of the more lax members of the People’s Guide staff may not go to such rigorous efforts to save a dime. But maybe that’s why we can’t afford to drive to Mexico this year and are forced to fly, like amateurs!

El Codo says:

No matter how you figure it, a gallon of regular gasoline in México costs the equivalent of three dollars and thirty five cents, and stops at Pemex pumps really can jolt a travel budget.

Let’s say you have a pickup truck or van and intend to do a colonial cities or beach trip and you figure that you’re going to put four thousand miles on the odometer south of the border. Your beast, undoubtedly, is a V-8 and you figure you’re getting 15-mpg, which is about average for a full-size vehicle that isn’t burdened with a tire squishing overload of needless gear.

Four thousand trip miles divided by 15 miles per gallon requires 267 gallons of gasoline.

267 gallons of gasoline costs 893 dollars. Eight hundred ninety three (gulp) dollars!

If you could only better gas mileage by a lousy ONE mile per gallon it would mean spending 837 dollars instead of 893. That’s a lot of tacos.

A two miles per gallon improvement means saving one hundred five dollars!

But sadly, achieving your vehicle’s top potential highway fuel economy is not always possible. Everything from short-haul jaunts to slightly less than accurate gas pumps are going to enter into the fuel mileage calculations picture. Rather than have all this jump onto your shoulders and force you to despair, you can take tangible precautions to minimize fuel expense.

  • Many states require a “smog check” to qualify a car for licensing. If your car has undergone the test within the last year, and passed, then you know for sure the engine is in good shape and tuned well enough that it will be as frugal as possible. Older cars without diagnostic on board computers (and CHECK ENGINE! lights) that live outside areas with mandatory smog tests can be robbing you blind at the gas pump. Call around and ask if someone can run a “check-only test” on your car. Instead of moaning about the price, convert the price into the cost of gasoline in gallons. You have to live with your car before and after the trip so checking a car does not qualify as a “Trip Expense.” A smog test is a superb way of determining whether or not your car is dipping your wallet. If the car tests out as being “OK” so much the better. When I did this for a friend, the car failed the test miserably. The culprits turned out to be bad spark plug wires and leaky vacuum hoses. His eighty dollar (twenty-four gallons of gasoline!) total investment has subsequently saved him many times that amount in improved mileage. In my book a “check-only” smog test is one of the best money-saving diagnostic tools in the business! But again, if your car is required to undergo this test annually, or has an onboard computer with dash warning lamp and stores self-diagnostic “error codes” then skip to the other stuff, below.

  • Buy tuneup parts cheaper and have them shipped directly to your home. This website figures out which part numbers your vehicle uses, then the company will send your order by parcel delivery to your doorstep. Name brand parts for a lot less!

  • Stop saying “lleno” (fill ‘er up) to the attendant and order your gasoline in liters. College educated Mexican drivers order their fuel by the liter for a good reason. Not every gasolinera has “erroneous” dispensers, but curiously those stations located along major travel routes seem to have the greatest number of errant pumps which deliver the least fuel for each peso. The error is frequently 8 percent and is never in favor of the motorist. Newer electronic pumps have sales (liters or pesos) orders entered by keypad. Watch the numbers flash on the pump. You’ll see your ordered liters total as it is being entered. There is absolutely no reason for an attendant to have to put gasoline in your tank the old-fashioned way (by standing there and squeezing the handle on the nozzle) other than topping off the tank after the nozzle clicks off automatically. Filling until the nozzle clicks off should be a totally “hand’s off” operation and if you see the attendant nursemaiding the nozzle (some non Pemex private stations in rural areas have the old-fashioned style of gas pump – in that case the attendant must squeeze the handle), after you’ve requested gasoline in liters, tell him to stop and go to another station. You are being cuckolded in a most brazen fashion. Also, if you see an attendant reach in his pocket and start punching numbers into a calculator after you order your fuel in liters, this too is a setup*.  If you want to fill up and you have no idea how much your tank will hold, simply order “cien litros” (see-EN lee-TROS) which equals 26 gallons roughly. Who cares? A motorcyclist can order a million liters, but when the tank is full, the nozzle shuts off like normal and the correct amount is shown on the dispenser (maybe four gallons, maybe less?). The tank is full and the amounts shown on the dispenser displays are correct. When Mexicans find an honest hometown gasolinera they might relax and order “lleno” or state a peso amount. But they will not order by peso amounts when away from home. (By the way PROFECO and other consumer agencies who check pumps, do so by specifying liters, NOT pesos when testing.)


*He is converting liters to pesos and will tally the result into the dispenser as a peso sale and try and hook you for a higher price. “Fill ‘er up” orders are punched into the dispenser keypad as a cash peso request, maybe a thousand pesos. The station owner knows PROFECO only checks pumps for liters-delivered accuracy. If you are in doubt about any of any of this, ask an expert – a Mexican motorist. Station owners hire employees who will collaborate. If all this makes you bristle, you’d better stop a moment and reflect. In the “old days” with old style gasoline pumps it was impossible to avoid tampered gasoline sales. Thank you lucky stars you now know (after being tipped off) what Mexican motorists know.


  • Check tire pressure. Door jam stickers suggest air pressure for the best possible ride comfort. You’ll find “max pressure and a number” stamped on the sidewall of your tire. This figure is for COLD inflation. Its OK to fill the tire to this pressure and then drive. Increasing and then maintaining tire pressure to the maximum as stamped on the tire can save up to 10% in fuel. I carry a tire gauge. The digital ones are precise. Keep valve stem caps on all tires. Carry spares. This avoids a lot of slow leaks. Also, those llantera “stick-type” pressure gauges can be horrendously inaccurate. Not long ago I re-checked “35 pounds” after the tire guy showed me 35 on his gauge and my digital gauge screamed 62! Consumer Reports says digital tire gauges are amazingly accurate – and you don’t need an expensive one.


  • On an extended trip I carry an extra air filter. Really dusty driving can clog a filter in just a few thousand miles. The Rock-Auto link above offers a chance to buy filters cheaper. I’d get an extra fuel filter too. Don’t forget wiper blades. Cars don’t get too good of gas mileage should they veer off the road in a downpour and smack into a cactus.


  • Make sure your engine’s coolant thermostat is not malfunctioning and keeping the engine too cool. This is a most sneaky way to lose five percent in fuel economy. The correct amount of heat coming out of the heater will be welcome in cooler climes.


  • Older cars and pickup trucks are pretty liberal about gasoline octane. But a few, newer, high-tech motors can be choosy as hell about what they want to eat. Fussy engines won’t need fuel laced with an additive like Chevron Techron® if you switch to made-in-USA Pemex Premium grade fuel sold in the red pump. But beware of spending money when you don’t need to. Most engines do fine on straight green pump Pemex Magna. Using Premium or additives when you don’t need to would be a complete waste of money. If you think you might need Techron®, buy it in the US.


  • Take your foot out of the carburetor.” Slowing down can save a lot of gas. When on an autopista (cuota) toll road, if the speed limit signs say 110 kph (68 mph), I’ll back my speed down to 60 mph and stay in the right lane. The reduction in speed can save one or two miles per gallon. Even if I were to stay on the road eight hours, and maintained an eight mile per hour increase in speed it would only mean being 64 miles further down the road at sunset – a little more than an hour’s travel time. It would take an awful lot of fast driving to add up to saving on a night’s hotel bill or a vacation day.


  • An out-of-balance tire can make ride comfort so unpleasant that a driver will automatically speed up or slow down to avoid the point where the jiggle is the worst. Have your tires spin balanced before you leave home, as only the most expensive tire places in the biggest cities in Mexico have a mere bubble-balancer. When the guy is doing the balancing, explain that you’re headed to México and ask him to mark the position of each tire on each wheel with his yellow wax crayon. When you get a flat and the tire is dismounted for repair, the llantera won’t lose the right spot. Mark inside and outside the tire and wheel for the best odds of keeping the marks visible. I write “O” and “I” on the tire. Outside and Inside. So the llantera can not mount the tire backward and lose the original balance points without you knowing about it.


  • The heavier you load your car, the poorer the mileage. Truck scales are common in the US and they charge way less if they don’t print out an official weight ticket. It’s smart to weigh your car or pickup empty, then return and compare after you’ve loaded it for the trip. You might find yourself dumping some of that “absolutely essential” gear. Loading a vehicle past the Gross Vehicle Weight limit on the door post emblem is just screaming for trouble – not only with gas mileage, but tire blowouts, brakes, overheating, transmission failure and vehicle handling and stability.


  • It isn’t always possible to avoid the following, but I try to miss cities during the morning and evening commute. Rush hour traffic can mean an hour or two of stop-and-go. This kind of driving just eats up gasoline. And time. And temper.


  • If you’re going to be haunting an area for awhile, park the car and forget about it. If the local market seems to be out of range for walking, maybe the market is well within range of a bicycle. Buy an old bike in the states, zip tie a plastic crate atop the rear fender, then lash the bicycle somewhere onto your vehicle. A bicycle will not block airflow to the radiator. There’s nothing like a three mile bike ride before dinner to work up an appetite!


  • If you see dew or dirt residue on your windshield in the morning, keep your gas tank topped off. Nearly empty gas tanks can accumulate around a teaspoon of condensation water vapor every day, and the water settles to the bottom of your gas tank in an ever growing blob. A quart of condensation water would require a gallon and a half of alcohol be added to a fuel tank of gasoline to absorb it. Alcohol plays hell with rubber gas lines, engine gaskets and fuel pumps. Skip the alcohol and keep your tank topped off.


  • If you pull into a Pemex gas station (called a gasolinera in México) and see a tanker truck dumping fuel, STOP! Don’t fuel up. Either go to another station, or wait 15 minutes after the tanker departs. Gas station fuel tanks have a horrible layer of sludge, water, rust powder and other contaminants sitting on the bottom. After the tanker stops dumping fuel, the awful stew has a chance to settle-out and clarify. Fueling when a tanker is dumping fuel is arguably the number one reason for getting a clogged fuel filter these days. Mexican gas pump dispensers do not have filters! Sure, new pumps come with filters, but the first time they clog up the station owner jabs a screwdriver through the element and screws the cartridge back on the pump. Rather than gnash your teeth at the seeming the misfortune of needing fuel at the same time a pipa is dumping gasoline, go have a taco, check the air pressure in your tires, scrub down the windows or daydream about how lucky you are to know better than to take on a load of contaminated gasoline.


An El Codo truism – Skeptics who have never tried ordering gasoline by the liter are the ones who yell that “it couldn’t possibly make a difference”.


Gas mileage is computed by dividing the amount of fuel pumped into your tank by the distance driven as shown on your odometer. To speed up and simplify the conversion of Mexican liters to US gallons, go online, GOOGLE Liters To Gallons Conversion Tool.


Copy on a piece of paper small enough to slip into your glove box a range of conversions that would be appropriate for your gas tank size. From one quarter total capacity to 3/4ths total capacity will work fine. You can also do this on your computer then print out the conversion. Use a clear Plastic Sheet Protector then slip the sheet under your seat.