I see that Exxon Mobil is now advertising on TV that they now have a cleanser in their gasoline to clean the valves. That put them on the top tier gas station list. They have been on the list for months, but this is the first time I have seen the advertisement.

I think back and can't remember how many years ago that Chevron put the techron cleaner in their gas, maybe the '80's.

click on any of the links on the page below for more information on what top tier gas is.

http://www.toptiergas.com/retailers.html

 

Having used bottom tier gas (almost exclusively) for the last 30 years and having owned cars, on average, for well in excess of ten years each I can say, without any reservation (nor any engineering or mechanical knowledge, mind you) that I don't think it's worth the premium.
My cars have never had any engine issues.
I love the discounters!

 

Haroldo, I think you have found some of the better discount stations to buy from. This was back in the late 70's when I bought Sello gas which was from Mobil. I used it for a few months. It was a low or minimum additive gas. People complained of hard starting engines, poor acceleration including knocking. The Sello stations in Dallas closed after a year of operation. This may have been before the government upped it's rules for a minimum cleanser to be added to all gasoline's.

Here were I live in new mexico we have a discount station just a block from the phillips 66 I buy from. For 3 cents per gallon I prefer to buy the phillips 86 octane.

Back in '99 when we moved out here from dallas I did try Fina, diamond shamrock and a save-a-mart station. All made the car a little slow starting and I lost a few mpg. The worse of any gas I ever used was the Walmart gas. Ours comes from Phoenix. Your walmart brand is different and comes from a east coast supplier. It took me two tanks of gas to get my car running good again.

 

I agree with you 100%!!! (except I can say that having owned cars for 40 years)...

 

Isn't the real test the mileage on our cars , not the years... I only drink top shelf alcohol and provide my TCH the same luxury- Top Tier Only...

 

Has anyone done an apples to apples comparison? I doubt additives (to clean the valves?) do much to add to the mileage. I'm an idiot, but either the spark plug ignites the fuel, or it doesn't, right? I mean, it's not that some gas explodes with more force than others. Or do I not understand the stuff.

 

My understanding is that the additives not only cleans the valves but also the rings, piston tops and most important the injectors.

I remember in the late 60's and early 70's when they took the lead out of the gasoline. The oil companies were trying to figure what was needed to replace the performance of lead.

It was the late 70's was when Chevron decided to start adding their Techron engine cleaner product in their gas to satisfy the governments demands to improve the no-lead gas. In the 60's you could buy a small bottle of Techron additive for $3 you could buy at their stations. Chevron still includes it in their gas. All the Oil company brands in the top tier list use a similar additive.

The manufactures starting around 1971 and throughout the 70's used cupped piston tops to help lower the compression for the not so good no-lead gasoline's of the time. They put additives in the gas which also produced a little extra power. The additive would cause a powder residue to build that would stick to the tops of the pistons. Before long on a hot day you could shut off your engine and it would diesel knock till you reached the front door of your house then the engine would would finally shut off.

About a year later the gas companies started putting in much better additives which resolved the dieseling and pinging problems along with more power. Gasoline's of today are much improved from the from the early 80's gas.

I average about 13 gallons per fill. It cost me 3 cents more per gallon for the top tier gas, which is only 40 cents more per fill. Not that much difference to spend for a nice expensive car.

 

By Mileage I meant the total mileage you have on your car when you change it out , not MPG. If you only drive 3000 miles a year then 10 years of usage is quite different than if you put 30,000 miles on your car(s) and keep it 10 years.

 

Additive packages help with a couple of related issues:

• Build-up of deposits in the intake tract , especially the back of the intake valves.
• Build-up of deposits on the injector, resulting in a poor spray pattern and atomization.

The valve deposits create issues with flow and turbulence. Bad spray pattern will create mixture consistency issues and result in 'too rich' and 'too lean' areas as well as poor atomization. Both of these issues will reduce efficiency, drop FE, and cause drivability issues.

Another issue, which most additive packages wont' really address, but which hydrocarbon mix impacts, is EGR valve clogging. Certain fuels will make carbon deposits worse - likely due to ring hydrocarbons. Combined with a poor spray pattern, EGR clogging will be a problem.

 

Lead tetraethyl was a cheap (and deadly) way of increasing knock resistance of motor fuels. It allowed refineries to increase gasoline yields from a barrel of crude relatively easily. It also had a property of lubricating the relatively soft valves and valve seats one got by simply machining a seat into a cast iron head (or block, back in the OLD days).

The lower compression of the 70's was partly a nod to the unleaded fuel, but also a cheap way of reducing NOx with the primitive carburetors and 'fixed curve' ignition systems. Remember, when you don't have a knock sensor, you have to tune for the 'worst case' or have the engine self-destruct. Yes, vacuum advance/retard strategy helped - but they were quite limited in their effectiveness.

The 'dieseling' was really due to the fact that carburators couldn't shut off fuel; you shut off ignition. Sometimes there were enough 'hot spots' to ignite the mixture. Another factor was that the emissions strategy called for higher idle speeds, which would contribute to the dieseling tendency. Fuels helped with the dieseling by being harder to 'compression-ignite' - i.e. higher octane rating.

As to improved - well, more in tune with modern cars. The old crocks still on the road may well have problems with modern fuels

• Vapor lock, which in the relatively high pressure of fuel injection is a lot less likely, but in the low pressure of a carburetor is quite likely
• Issues with old fuel pumps and hoses, necessitating a rebuild
• Issue with excessive water in fuel due to alcohol.
• Issues with fuel mixtures. Modern engines will lean out or enrich the mix based on O2 sensors - the old crocks cannot. This is especially bad with ethanol, as it effectively 'leans out' the mixture.