7milesout

You're not comprehending. I DO NOT buy the cheap stuff.

roadfrog

Splitting hairs. Sometimes, good enough, is really good enough, especially if it saves you money. My Chinese winter tires are a direct copy of the Michelin X-Ice, but cost half as much. I've run them for 5 Winter seasons now and they still have tons of tread and stop on a dime in any condition. This applies to a lot of my consumer choices. Obviously, using something that has the potential of harming your car (such as this topic regarding fuel), is "penny-wise, dollar foolish". I'm just not convinced that using 87 octane is. However, that's why I love these discussions....ya never know what you might learn!

aypues

Be very careful with replicas. Usually they are not engineered with the same safety in mind. I would never buy a replica tire or wheel.

Look at this video:
http://www.motorauthority.com/news/1...a-wheels-video

Chuckinnj

Well said! ^^^^^
I learn something every day on these forums and most of the time it ends up costing me money. EG: Saw the post about the Prestigious Society module the other day and how EZ it was to install so I had to buy one........ Now I will have to go "check out" some Chinese winter tires!

Oldfart

I own a scanner in addition to other things it also can read timing. Some of you think that when you use premium knock sensor doesn't work "overtime" and if you fill up with regular it will work "overtime".
I was absolutely surprised to find out that the most straggling condition is at idle. While it feels and looks like RPMs are steady timing is all over the place at idle regardless of the type of gas.

"Engineers know better" argument.

For typical consumer engineers might assume the vehicle to be operated between -20 F to 100 F. Altitudes 0ft to 12,000 ft. Weight loads +0lbs to +1,000 lbs. So obviously compression ratio is not the only mechanism at play. For example I leave for work at 7am and outside temperature is +60F, I will easily get away with using regular but at lunch time when my buddies want to get a ride in my "limo" outside temperature got to +85F in addition I have extra 700+lbs. With this conditions it is much more difficult for the car to get going from stand still even premium gas might not be enough but it is the best I can get. Engineers cannot write separate fuel manual for different type conditions that is why premium is required because it will be good enough for all conditions while regular will not.

As a person I do not know if I am taking my coworkers to lunch today or not or what is the weather is going to be like so I just fill up with Premium but as a car enthusiast I like to know how things work.

satiger

iTrader: (1)

I hope this helps. Sorry about long post but thought of clarifying some myths/notion around octane / knocking / additives.

Nowadays, gas is made up of hydrocarbons (mainly paraffins, naphthenes and olefins) produced in a catalytic cracker or reformer. The refinery process breaks the crude oil’s large hydrocarbon molecules into smaller ones by vaporizing them in the presence of a powdered catalyst (an absorbent mineral such as zeolite). The blend varies depending on where the crude came from (sweet vs sour crude), the refinery equipment used, and the grade of gas being produced.

Additives are included to reduce carbon build-up inside the engine, improve combustion, inhibit corrosion and allow easier starting in cold climates. Fuels that meet the requirements for “Top Tier Detergent Gasolines” (a voluntary standard endorsed by BMW, General Motors, Honda, Toyota and Volkswagen) contain more detergent in their additive packages than the minimum required by the authorities. I had responded to another thread in this forum with similar info.

A higher octane rating allows an engine to use a compression ratio of, say, 12-to-one instead of a more usual ten-to-one. The greater the compression, the higher the temperature within the combustion chamber. And the higher the temperature, the greater the thermal efficiency and power produced. In a nutshell, high-compression engines designed for performance need high-octane gas.

Knocking happens when the air-fuel mixture in the cylinder detonates spontaneously before reaching the top of its compression stroke, the rising piston confronts a wall of rapidly expanding gases from the explosion, which attempt to force the piston back down the cylinder. The stresses caused by suddenly trying to reverse the rotation of the engine can become high enough to shatter the pistons, connecting rods and parts of the crankshaft. Lower octane grade gas has lower combustion temperature. In other words, lower octane gas will combust at lower temperature than higher octane gas. Thus, lower octane gas will cause pre-mature combustion (with out spark plug ignition) with higher pressure inside the chamber pushing the piston down before completing the cycle.

A fuel with a higher octane rating is less prone to auto-ignition and can withstand a greater rise in temperature during the compression stroke of an internal combustion engine without auto-igniting, thus allowing more power to be extracted from the Otto-Cycle (yes Otto cycle).

Knock sensor are designed to catch such pre-mature combustion and retard the timing - delay the spark plug ignition. But when engineers design high compression engine, they expect knock sensor to work on exception basis than on regular basis. Even though knock sensor prevent engine knock, it won't prevent quick combustion and the result of high pressure builds inside. It is not good for engine in long run.

• If manufacture *recommends* premium, better be safe than sorry
• Average cost difference between reg vs premium is around .30 - .50 cents
• Considering 15,000 miles with 25 mpg, annual cost saving is around $300
• There is quality difference between non-branded vs branded vs Top Tire Gas

ChrisK

iTrader: (1)

"Premium unleaded gasoline with an octane rating of 91 (Research Octane
Number 96) or higher required for optimum engine performance. If 91
octane cannot be obtained, you may use unleaded gasoline with an octane
rating as low as 87 (Research Octane Number 91). Use of unleaded gasoline
with an octane rating lower than 91 may result in engine knocking and
significantly reduced performance. Persistent knocking can lead to engine
damage and should be corrected by refueling with higher octane unleaded
gasoline."

Fuel information

You can interpret this on many different ways. In my book, use regular only if premium is not available and only temporarily. To keep you engine running as designed and clean use premium gasoline only.

Devh

Very good information.
Yes it can be misinterpreted but this statement says it all.
"Use of unleaded gasoline with an octane rating lower than 91 may result in engine knocking and
significantly reduced performance"

Who still wants to take a chance, I won't if Toyota cannot guarantee that I will not have knocking with octane below 91.

SW17LS

You don't understand my point. If your chinese winter tires are truly a direct copy of the Michelin X-Ice and cost half as much (I would have a hard time believing that knowing what I know about the quality of chinese merchandise) then that would be a value...you are paying less and getting the same.

The argument of 87 vs 93 is not the same argument, because 87 and 93 are not equal. The car might run "okay" on 87, but its designed to run on 93 and runs best on 93...meaning when you run 87 you are paying less...and getting less...which is not a value.

Another example. It's like buying a nice higher spec HDTV and not paying for HD through your cable provider. Yeah you can watch TV, but if you were going to cheap out on the cable negating many of the benefits of your new TV why did you buy the nice TV?

Broker404

I don't believe this is true. If this was the case, hybrid cars would not exist; and non-hybrid cars that stop and restart their engine every single time you come to a stop would not have that feature.

I stop my engine anytime I come up to a familiar long traffic light that is going to be more than a minute or two.

I hate the whole notion that exists that was maybe true before fuel injection(like before the 1980s), which is that you should leave your car on if you're only going to be a couple minute, because you'll spent more gas starting an engine than to leave it running for a couple minutes. This thought process still exists today even though it should have died so long ago. I read an article once (trying to find a link now) that said researchers tested several different types of fuel injected engines, including older, high mileage engines from the early 90's, and brand new, fuel efficient engines, and found that even the least efficient engine (high mileage 90's American V6) would save gas if you were going to be stopped for any more than 6 seconds. The brand new, direct inject engines were so efficient that the act of starting them literally didn't use ANY more fuel than if those cylinders had spun just as many times at idle or neutral.

I see people idle their cars all the time for no reason... even during spring/fall when they aren't using heat or air conditioning. I understand that people just don't care about the environment and there's not much you can do to change their minds, but why do something that doesn't benefit you whatsoever, cost you money, puts wear on your car, pollutes, all for.... ?

Oldfart

No amount of arguments will change what people believe in.

By the way I was not making an argument about fuel savings I was saying that starts damage everything starting from battery, starter, alternator, pistons, cylinders, rods, heads.

When I was running with scanner plugged in all the time this is what I’ve noticed.
Whenever I shut off car and restart it within a few minutes during hot weather I’d say 90 F and above my scanner would report significant timing difference from the norm. My own unscientific explanation is that air inside intake manifold and inside air filter compartment cannot cool down and gets very hot from engine heat. Hot air + hot head + high compression do not mix well even for split second it is damaging. But again we are talking about specific condition – hot weather.

Not so long ago cars didn’t have electronic ignitions everything was mechanic, ability to advance/retard timing is one of the greatest improvements.

Many auto makers use same engines for regular cars and for luxury brands with different fuel type requirements. People believe that engines are tuned differently. Why would engineers tune same engine different? Engineers can change geometry but they cannot change chemistry (fuel regardless of octane rating burns with same speed) so optimal performance at which mixture is fully burned is 20 degrees after top dead center (ATDC). Why would engineers intentionally tune one engine out of it optimal performance?

In order to boost horse power most commonly engineers slightly redesign manifolds (again changing geometry not chemistry), which usually results in minuscule increase in HP somewhere between 5-10.
Now HPs are measured at peak performance at high RPMs (which are not normal driving conditions for regular consumer). During those few seconds engine needs as high octane rating fuel as possible. I filled up with 100 octane and even then my engine still would pull timing with RPMs above 5000.

GregCon

When I bought my LS, I was coming off a GS and my wife had an Infiniti, both of which called for 93 octane. We had used 89 octane for years with no issues.

So I used 89 in my LS for several tanks. I noticed it was running lousy...a definite surging rather than a smooth acceleration, even under light throttle. The car was under warranty so I took it to the dealer. After a couple hours, the service guy called me to his desk and said the problem was that I had been running 89 octane gas. I informed him with quiet indignation I had done no such thing and there must be some part under the hood that needed changing. He produced a several page long printout from their technician which had a bunch of mumbo-jumbo that indicated they had done a bunch of computer-based testing. At the bottom of the last page, it said something like 'Fuel incorrect - 89 octane - 93 octane required'.

I took my car home and began using only 93 octane and it's run as intended ever since. But only after surmising to the tech, of course, that my wife must have put the 89 in it so as to support her penchant for shoes, purses, heroin, etc.

GregCon

As for why would en engineer tune an engine differently there are several reasons....for example, the same engine used in a Camaro might be tuned for max HP but in a 1 ton truck they dial it back so as to prevent it from coming apart. Pushing a 7,500lbs dually towing a 12,000lbs trailer for 45 minutes up a mountain road is way tougher on the engine than anything a Camaro driver will do.

Moreover, I used to have a Dodge truck (1999) which, Dodge bragged, had an adaptive PCM that would 'learn' how you drove and tailor the engine/transmission tune accordingly. In other words, if you drove like Granny it gave you earlier and softer shifts and a less aggressive timing curve. The 'learning' took place over time, in either direction.

All of which was really stupid because it essentially punished you for Granny-like driving. For example, if you cruised around with a soft foot usually (to save gas and wear and tear), then you came to a stopl ght and wanted to race a Mustang, you were in trouble because you weren't getting all the power or shifting that you could have used right then.

aypues

I don't think 93 octane is required. They don't even make that in CA so I use 91 which is Premium fuel here and it runs fine. I've never put in anything lower...want to keep it running a long time - at least til 2020 when I'll be ready for a new(er) car.

Slvr surfr

iTrader: (1)

Better value was/is a 92 LS vs. an 92 S-class. Cost less but you got more car.