Premium DOES make a difference

[theprodigy79]

Premium CAN improve performance if it is what the car was intended to run on... The ONLY thing the additives in higher octanes do is make it harder for the fuel to combust... meaning less chance of pinging or knocking... If your engine is pinging or knocking (caused by premature combustion), a higher octane will solve that, in turn improving fuel efficiency and performance... If your engine does not ping or knock with 87 octane, upgrading to 89 or 93 octane (or 91, 92 or whatever in other areas) should not make any difference... If your car pings or knocks (even in the slightest) with 87, and upgrading to mid-grade cures it, there is no need to go further... if neither regular or mid-grade solve the ordeal, high grade is the way to go (and you will see an improved fuel economy and performance throughtout the entire range of fuels...) Of note, I believe both the 04 Solara manual AND (I know for a fact) the TSB for throttle lag state clearly that high-grade is recommended... They do not say that it's required... but I personally will use no less than 93 Octane. I highly doubt that the car would ping or knock with any lower (at least with mid-grade), however the $.10 a gallon difference between it and mid is insignificant to me and well worth keeping my car running optimally...

[slingshot]

I agree that 21mpg city is way too optimistic. 18mpg city and 29 highway is alot more like real world all city or all highway driving. The highway number though would be with cruise control on.

[angelo]

It seems that all the confusion in the power ratings for the 2006 models is coming from the new certified SAE ratings procedure. Honda engines also took a dip in power ratings - Acura TL is down to 258 hp, RSX type is down to 201 hp...

[mmcdonald]

As I posted in a related thread on this issue:

"The Octane rating is used for one thing, and one thing only: to measure the percentage of octane to heptane, or the ability of the gasoline mixture to mimic a similar octane/heptane ratio.

It just so happens that those ratios of octane to heptane have a generally accepted ability to resist spontaneous combustion at a given compression ratio.

This does not take into account the ambient air tempreature, the load on the engine, and the heat already generated by the motor from previous pre-ignition (ping/knock/detonation/spontaneous combustion).

The Solara motor (V6 in my case) does have a knock sensor that compensates for having to use (against the manufacturer's recommendation) sub-premium fuel. This is not recommended because of the following:

As to the assertion that increasing octane ratios does not result in higher mileage OR better performance, the purpose of high octane fuels is that they enable high compression ratios to be used. Higher compression ratios give increased power output and improved economy (assuming the same engine displacement and other aspects). The octane number requirements for a given compression ratio vary widely, but typically a compression ratio of 7.5:1 requires 85 octane fuel, while a compression ratio of 10.0:1 requires 100 octane fuel. The V6 has a 10.8:1 compression ratio, so the knock sensor is already working overtime.

Raising the octane level of your fuel will primarily help prevent knock. If your engine is not currently knocking using regular, you won't see any significant advantages of using higher octane fuel. On the other hand, if the engine is designed from the beginning for higher octane fuel (and ours are!), it will have considerable advantages in power and economy. Since the knock sensor retards timing to prevent spark until after TDC, you are losing a percentage of the power stroke to retarded timing with lower octane ratios, and thus losing the full power stroke per cylinder of fuel burned. Since you are not getting full power, you therefore have to use a greater quantity of gasoline to go the same distance. Again, since you are losing a part of your power stroke to retarded timing, you are losing the engine's ability to completely burn the fuel, so you lose power and mileage again.

Over time, you also clog up the exhaust channels with partially burned fuel (from the cylinder head up to the catalytic converter, which has to work overtime). This clogging constricts the exhaust channels and will then result in lower power and inefficient fuel burn.

Lemme ask you: Why do race drivers use higher octane mixtures if there is no power advantage?

Compression, which we got, requires higher octane fuel, or you end up being retarded!"

In this case, if you are not racing around as you commute to work all week, then you probably don't need a higher octane fuel. However, before I got my ride I calculated the cost of paying for premium over regular assuming $.20 per gallon price difference, 25K miles per year, and 25mpg. It is about $200 per year. However, I get closer to 30mpg during the week, but I drive closer to 30K per year. Anyway, it makes sense for me on the highway, and the cost difference is negligible. So why quibble with the manufacturer's specs?