codeman720

I have a 2003 4Runner with a V-8, We just bought it about a month ago and now notice that when it's started in the cold, there is a little ticking for the first few minutes. I just got it checked by mechanic, looks good, changed oil to synthetic, the truck runs beautifully smooth. I was told it may be from not using premium gas, does that make sense to you guys?..

mastacox

It's doubtful that gas is to blame for cold start ticking, that's more likely what weight oil you are using. The newer toyota engines (at least the V-6 1GR-FE) is notorious for having loud fuel injectors too, that might be what the ticking is.

Higher octane gas will help prevent spark knock (ping), but if you're running 87 and aren't having a problem, you're probably ok. Does your users manual call for premium fuel to be used in the engine?

91TPU

i doubt that toyota calls for anything other then regular 87 on that vehicle, and i doubt the cold start ticking is caused by lower octane gasoline...ive run every type of gas, and usually stick with what the factory says to use...if they say run 87 i do, if they say run 91 then i run that....only time i switch is when i go offroading i run higher octane so that i have a lil more pep in the engine...

mastacox

I wouldn't be suprised Toyota engine or not. Many newer engines use higher compression to increase efficiency (increases both power and fuel consumption at the same time), and as such they require premium gas to keep ping under control.

91TPU

i agree, but vehicles like that seem to be more of cars, then a v8 suv

91_4x4runner

My 92 SC400 (has the 1UZ, the precursor to the 2UZ) calls for premium gas, and it's only got a 10:1 compression ratio. It wouldn't surprise me at all that the '03 Runner would call for premium.

I know that the 1GR-FE retards timing for lower octane gas and advances it for higher octane (you can supposedly see an actual increase in power).

Dan.3

It goes for SUV's and trucks as well. It all depends on what the manufacture recomends. For instance I had a friend of the family that had both a navigotor and expedition (both the same thing obviously). The navigator required 93 and expedition required 87. The navigator had better gas milage. I dont know how much better though. Maybe a gallon or two. I know if the vehicle requires 93, that is for optimal power and milage. If the vehicle requires 87, then is no point to put in a higher octane because it will not make a difference at all. The computers optimal setting is that specific octane. If there is a difference it still isnt worth the price of the higher octane because the difference is so small. On econmy cars you could damage stuff because of running higher octane. On cars the require 93 and going to 87 is fine, but you will notice a decrease in fuel economy and significant decrease in performance.

mastacox

The specifications for the 2006 4Runner says recommended gas octane is 91 for both the V-6 and V-8. Both engines also have a 10.0:1 compression ratio. Read for yourself at the Toyota Pressroom. The 2003 4Runner's specifications also call out 91 octane for both engines (even though the older V-8's compresison ratio is "only" 9.6:1 Linky.

That being said, guys at TundraSolutions.com say that both the V-6 and the V-8 run fine on regular 87 octane. My take is that try 87 to see what happens, but if you notice a significant degredation of power (evidence of heavy timing retard), or it's hot (over 90*F) you'll probably want to run premium. Also, always be on the lookout for ping.

mastacox

You've got that backwards. Running regular in a car that requires premium (especially high compression and forced induction applications) can definitely damage the engine. For an economy car that "requires" 87, nothing will be damaged by using 91, you'll just get a little bit worse mileage.

There's nothing magical about a gasoline's octane rating, it's just a measurement of how much ethanol is in the gasoline. More ethanol means the gas will combust at a lower temperature, and help prevent ping.

Dan.3

what could you damage? The computer adjust for lower octance. I sould see something getting damage on a high performance engine that is carbed, but not for electronically controlled.

rdlsz24

Run premo if your manual calls for it or you have forced induction. Otherwise stick to the "cheap" stuff.

Rob

mastacox

The computer can only retard the timing so far, and in many cases it isn't able to adjust it enough for large amounts of ping. That, and cylinder combustion temps are higher with regular gas than they are with premium, which can make or break an engine tuned for 91.

Sounds like good advice to me.

Dan.3

[QUOTE=mastacox;50488672]The computer can only retard the timing so far, and in many cases it isn't able to adjust it enough for large amounts of ping. That, and cylinder combustion temps are higher with regular gas than they are with premium, which can make or break an engine tuned for 91.



Gotcha. I was always under the impression that the higher octane burned hotter but your answer does make sense. Thanks

mastacox

Higher octane gas burns relatively cooler because it has more ethanol in it.

Mark in MD

I have the 4.0 in my new Tacoma, otherwise known as the 1GR-FE. My manual says this exactly:

Fuel type: Unleaded Gasoline, Octane Rating 87 (Research Octane Number 91) or higher.

I thought higher octane meant more flammable, more highly combustible, and therefore you get more powerful. Is this not correct? And if it is correct, why would it be favored when air temperature is over 90 degrees F?

Does anybody know the difference between "Octane Rating 87" and "Research Octane Number 91"?

Again, I ask: I thought higher octane meant more flammable, more highly combustible, and therefore you get more powerful. Is this not correct?

X-AWDriver

Actually higher octane fuel is more stable,less volitile and will only ignite at the right cylinder pressure. There is no horsepower gain from higher octane gas but it allows for your particular setup in forced induction to make that extra horsepower without pre-ignition which is also reffered to as detenation..

AH64ID

On the new tacomas (1GR-FE) the engine senses the gas, via ping, and retards timing, It has enough leeway that it runs fine on 87, but gains performance with 91. All the hp rating are on 91, so you dont make 236/266 with 87. but thats still plenty for me. On both my 4.0L's I run 87 day to day, 89 when towing, 91 when towing above 4K.

One thing I have noticed on my 03 is that on cheap 87, costco, etc, it will have a stutter problem at idle sometimes. Thout it was the ECU issue that caused the rotten egg smell, took it in had that done, still does it when running costco gas, but not chevron?? Toyota has no clue, you guys have one?

91TPU

your familiarity with newer vehicles supercedes mine...good posting...you know what you are talking about

mastacox

The 2006 Tacoma Sepcification calls out 91-octane as the "recommended fuel." I'm not sure what the difference is between "Octane Rating" and "Octane Number" as stated in your manual. Like AH64ID mentioned, the 4.0 seems to run fine off of 87 octane, but you will not make the manufacturer-spec horsepower and torque because the engine has to retard the timing with lower-grade fuel.

Not really, all the octane number really is is a qualitative value describing how much ethanol has been added to the gasoline. Ethanol has a nice cooling effect during combustion by lowering the stoichiometric combustion temperatures for the fuel mixture; this in turn helps your engine's cylinders stay slightly cooler and less prone to ping. Therefore, because the engine is not knocking, designers can go for higher compression ratios as well as more spark advance to make more power. In addition, more ethanol helps raise the flash point of the fuel, so even if the cylinder was at the same temperature as with 87 octane, the fuel is less likely to spontaneously combust in the cylinder before the spark plug ignites it.

I just threw the 90 degrees figure out there, but the general problem is that the hotter the ambient air temperature is the hotter your cylinder will be, making your engine more prone to ping. The hotter the ambient air temperature is, the more you engine will have to retard its timing to prevent ping.

In Tucson, on the really hot days (110 degrees plus) some people I knew had to run higher octane gasoline to reduce spark knock in their engines, even though the manufacturer spec called for 87 octane. Stop-and-go traffic in the desert is viscious on an engine...

91_4x4runner

Ping is the air/fuel mixture igniting before the ignition spark is generated... By higher octane fuel being less volatile, it is less prone to ignite before spark....

(Ping can/will eventually result in engine damage).