My mechanic says Costco and the grocery stores sell gas without the good additives, which can do terrible damage to your engine. Does anyone have similar knowledge or opinions about this?
Your mechanic is an idiot…Find another mechanic.
The independents buy their gas from the Major oil companies with the EXACT SAME ADDITIVES they use. There is NO DIFFERENCE what-so-ever
Gas is gas. Use the proper octane (eg regular or premium if required) and don’t give it another thought.I have never cared where I bought fuel and have owned three vehicles into the 200-250k range without a single problem related to fuel or fuel system.
Costco and other “non-branded” gas stations sell gas that meet federal requirements for detergents, octane and purity. That said, some major brands provide different, and possibly improved, additive packages that go beyond federal minimum requirements. It may be beneficial to use a major brand like Shell or some other Top Tier gasoline, but from 20+ yrs of experience, I can tell you that discount gas I purchased has never caused damage to my engine. I can also tell you that the two times in 30 years that I could confirm that I had water in my gas, it was from major brand stations. I also believe today’s monitoring systems and required storage tanks are much better than they were in the 60’s and 70’s, so the odds of getting bad gas is much smaller today.
here in england,our supermarkets sell petrol at a few pence per litre less than the “big brands”,such as shell,b.p,etc…but it is base fuel with no additives,so personally i always use a named brand of petrol because they contain detergents that help to keep your engine,and fuel injectors clean,so that your engine performs at its best.the cheap fuel wont necessarily do any damage,but over time there will be carbon build up,reducing engine power and economy,so its worth spending a little more for the sake of a smooth running,efficient engine.
wow - thanks to you all who responded so quickly!
I don’t know about your grocery store gas, but we’ve used Costco gas for many years and never had a problem.
How come when I fill up at the grocery store (Cub Foods in MN) do I get a bad sulfur (rotten egg) smell from exhaust? It is a less than year old station. It doesn’t happen with other off brands or name brands. Just curious.
Homer, I think you’re breathing too many of those fumes. Gas is gas is gas. Here in Des Moines, Iowa, there are two pipeline terminals - a BP and another one - Magellan. The BP stations buy from the BP terminal, all the others buy from the Magellan terminal. Every single station in Des Moines (except BP) buys from the same place. Sure, additive packages are different for some retail locations, but not enough to make any noticeable difference to the driver.
Are you quoting a test from a government source as to the make-up of supermarket gas?or is this just talk around the table?
mary in Denver,
You need to make up your own mind about the gas in your area. Try different brands of gas and use the one which gives you the most miles per gallon (MPG). Use the octane and maintenance schedule in the owners manual and your car will last a very long time. Its the “ounce of prevention is worth a pound of cure theory.” There is difference in gas and it is up to you to find out which is best for your vehicle.
Good luck
caballero
Never any troubles with Albuquerque Costco.
Mary; your mechanic is a chauvenistic jerk; other posters call him an idiot, but he really knows that ALL gasolines sold in the US have to contain a certain number and amounts of additives! As others pointed out, the additives just differ very slightly between companies. But he thinks he can spout this nonsense to a woman “who will believe anthing!”.
My Costco here does not sell gas, but I do buy gas from a local grocery Cooperative. In France, over 50% of all gas is sold by grocery and department stores. I would buy Costco gas if I could, and, unlike your “mechanic”, I am an automotive engineer.
because cheap gas has more sulphur in it,and the catalyst on the exhaust system is burning it off,hence the rotten egg smell!! use quality gas from a big brand ,such as shell,and you will be fine.
in england last year,cheaper supermarket petrol actually caused damage to 1000s of cars oxygen sensors,causing them to break down all across the country.why do people put the cheapest,crap in their fuel tanks?i use only descent brand fuel,because my ?12000 ford deserves it!!the cost diffrence is only a pound per tankfull,so why risk damaging your engine with the cheap stuff?especially in the usa where your petrol is so cheap!try paying the equivalent of 10 dollars per gallon,like we do!i only use shell,or b.p.
VERY TRUE.
check your milage and you will soon see.
Stephen - are you citing proven scientific data in your post, or anecdotal, heard-it-at-the-coffee shop talk?
First of all do yourself a big favor and find yourself a new (better) mechanic. In America, the smaller gas companies buy all of their gas from the bigger gas companies. Focus on buying the correct octane for your car, and not where you bought it.
@homer2804 - what you smell is your emissions system not working properly, or a defective catalytic converter. Your car may be running to rich caused from a bad O2 Sensor, or even something as simple as a vacuum leak. Take it to a mechanic, just make sure it’s not the same one the original poster goes to (sorry Mary couldn’t resist) 
Buy the cheapest gas that meets the minimum octane requirements for your car. As long as they look after their storage tanks, it doesn’t matter where it comes from. For several years, I bought gas from a neighborhood bar that had a couple of pumps out front. My cars ran fine on it. Recently, I have been buying gas from Sinclair stations because they give me a 5% discount if I pay for it with their Master Card.
The only difference in gas I have ever noticed is between two Sinclair stations three miles apart. One of them has stickers on every pump that advertise 10% ethanol. The other sells E-10 only from pumps labeled as such. I think I may be getting 1 or 2 miles per gallon more now that I am buying gas that I am sure contains no ethanol.
its just a well known fact in england some petrol companies use more sulphur than others,people have complained of a rotten egg smell,and have been advised to switch brands of fuel,which normally cures the problem .i personally use shell v power 97 octane and ive never had a problem.