i know it sounds crazy, but you can actually wear out your engine quicker by changing the oil (and filter) too often! Let me explain. the service intervals for the oil changes are decided between the oil filter, oil manufacturer and the engine manufacturer. From this, the filter manufacturer will design a filter that will pass a particle size that satisfies the engine manufacturer. For the filter to have a reasonable service life , the filter generally starts off with 'holes' that will pass particles just slightly bigger initially, but as contamination builds up on the filter, the filter starts to work as designed, then as it ages, the oil passing through it is much cleaner than when the oil/filter were changed as the dirt on the filter causes the filter to trap even smaller particles. So if you change your oil/filter too soon ,you are exposing your engine to particles of a much greater size than if you left the oil in longer. Please, don't waste your money by exceeding what the manufacturer has stated, they know best, they have done the testing. The same applies to any filter including your air filter, changing them too soon is killing you engine (and pocket) with kindness

 

But are completely oblivious as to how an OEM works.

 

If the intake valves are only being bathed in air, it seems unlikely that they would coke up except on the inside of the combustion chamber. Which is what spark ignition engines have been doing from the beginning - particularly if they're running rich.

An intake port filled with carbon compounds suggests the engine breather oil recovery system has failed - rather than the design of the fuel delivery system or oil change intervals being at fault.

Although, the failure of the oil recovery system may be more likely with infrequent oil changes...

 

91AKI appears to be the direct equivalent of our lowest fuel rating - 95RON.

Supermarket fuel stations may conform to this while - possibly - using constituents that attack the seals of fuel injection systems...

 

That's more or less correct, a 4 point spread between RON and AKI. Again, octane rating has nothing to do with the type or volume of additives.

Supermarkets get their fuel from the same refineries as the name brands. The only possible difference are the additives, but there is scant evidence that they are inferior in any way.

 

Yes, coming out of the refinery and at the distribution center, each grade of gasoline is the same.

My brother owns a tanker business in Georgia that picks up fuel at a distribution center and makes deliveries to service stations for all brands. When one of his drivers picks up a load for a Shell station, the Shell additive package goes into the tanker before filling it. The additive packages for the other Top Tier brands are probably similar, but each one has a different package.

It is true that non-Top Tier fuels (Sunoco, for example) may have detergents and other additives that are every bit as good. The problem is you don't necessarily know that.

My brother's company may deliver fuel to Bubba's Gas in Bumpkinville, which may have no additives. The purpose of the Top-Tier program was to convey to customers they are getting fuel with state-of-the-art additive packages that are agreed upon by a number of major engine manufacturers.

 

Spot on. The problem is that even the best of the top tier brands

1) makes little difference in performance or fuel economy as laid out in the recent AAA test when compared to Bubba's gas.

2) makes no difference at all in GDI engines where the fuel and it's additives never see the intake valves.

 

It may be that you need to review the layout of a spark ignition combustion chamber - unless you're talking about the the back of the valve head and valve stem...

 

Yes, that's exactly what we're talking about. This is the area of concern on GDI engines.

 

Mikey,

With regard to your #2, I agree for reasons that have been discussed above, that GDI engine valves don't get the benefit of fuel additive baths.

With regard your #1, the recently published AAA study arrived at quite a different conclusion:

Key Findings:

1. The test engine operated on a TOP TIER gasoline averaged 19 times fewer intake valve deposits than when it was operated on non- TOP TIER gasoline. (based on the ASTM D6201 test - TOP TIER gasoline averaged 34.1mg of deposits per intake valve versus non- TOP TIER average of 660.6mg)

2. Based upon secondary research findings, long-term use of a gasoline without an enhanced additive package can lead to reductions in fuel economy of 2-4%, drivability issues, and increased emissions.

Now, granted those key findings pertained to the testing done on a port fuel-injected engine, and we agree that GDI engines don't benefit.

Link to AAA study:

https://s3.amazonaws.com/association...rt-FINAL-1.pdf

 

There are some great illustrations of port-injection vs. DI in the AAA study (pgs. 9-10) linked above that you might want to review. That should show you what we're talking about.

 

Overlap on the intake cycle, and on the F-Type it may be particularly rich
due to the fueling curve to achieve the snap, crackle, pop effect.

Gas as solvent will also help out with engine breather fumes,
but nonetheless, wherever it comes from, the problem exists.

 

Again we agree.

2-4% difference is, uhh how you say in Engleesh- chicken sh*t.

A car getting 20mpg on top tier gas will get (at worst) 19.2 on Bubba gas, if Bubba gas actually exists and is used consistently enough for the lack of additives to have an effect.

Not sure if you've seen the BP ad with the car dragging the anchor


Here's the disclaimer at the bottom of the US version, in tiny little text:

"Ordinary Fuel refers to minimum detergency gasoline. Dirt refers to deposits on critical engine parts. Requires continuous use over 5000 miles. Restores an average of 3 - 5 miles per tank that had been lost due to deposits. Based on fleet testing representative of the U.S. car population. Fuel economy can be affected by many factors. Benefits may be more significant in older model vehicles."

https://mybpstation.com/fuels/invigorate

Are you as impressed as I am?

 

That is really old technology. Back in the late '80s we began injecting the additives into the gasoline metering system as the fuel was loaded onto the tankers. Since then, I'm fairly certain all of the major terminals have been using the same technology. Our tier-one clients typically all had their own proprietary packages which were stored in drum racks, and some of the clients (typically independents) waived the use of additives to save the couple pennies per gallon of gas. This is just a side bar...please carry on.

 

Yeah, OK, same thing, and it's been a long time since my brother and I discussed the nuances of how additives are mixed with the fuel his company delivers to gas stations. :-)

 

An oil catch can for the engine breather seems like a more likely fix.

Also, I would note that on a previous supercharged car, the 'Rice Crispy' effect was a byproduct of cooling the exhaust valves on overrun using fuel.

 

I have an 'oil catch can' to install on mine but have not gotten around to it. For Oil changes I don't have a hard and fast number, but tend to change after about 3 thousand kilometers for the first and around 10 thousand after.

Shell 91 is the fuel I use 99% of the time as it does not have ethanol and as far as whether or not its a waste of money to buy top tier fuel.. I don't really care as I prefer to use the best I can get.

Same with the oil catch can.. lots of opinions, but I like the idea of it, so I'm doing it.
Lawrence