Gas grades, Premium vs. Regular comparison notices

[KidVermicious]

You are simply wrong about this. The Toyota technical training material for the OBD I engines (among them the 3vze) states "The Knock Sensor detects engine knock and sends a voltage signal to the ECM. The ECM uses the Knock Sensor signal to control timing." This has been true ever since Toyota introduced multiport, computer controlled, fuel injection.

The '94 has a diagnostic data stream that comes from the ECU via the diag port. With a little bit (OK, a lot) of programming, you can read that data stream and see, among other things, what the ECU is doing to ignition timing as engine load and rpm vary. It's obvious the ECU knows all about the ignition timing, and is in complete control of it. There is no open-loop vacuum or centrifugal ignition advance such as we had on older engines. It's all done by the ECU.

I have studied the 3vze engine control system in detail for the past 5 years. I'm not guessing here, I know I'm correct on this.

You're going to have to bring some proof for an extraordinary claim like that, because you're the first person I've ever heard claim that the 3VZE can take advantage of premium fuel. The 3VZE has a very primitive knock sensor and when it triggers, the ECU puts the timing in limp mode to prevent knock. I suspect you're conflating that response to the knock sensor with the timing advance that any electronically controlled ignition executes as throttle input and RPM vary. But the signal from the knock sensor is not sophisticated enough to let the ECU do what you're claiming.

 

[RonJR]

You're going to have to bring some proof for an extraordinary claim like that, because you're the first person I've ever heard claim that the 3VZE can take advantage of premium fuel. The 3VZE has a very primitive knock sensor and when it triggers, the ECU puts the timing in limp mode to prevent knock. I suspect you're conflating that response to the knock sensor with the timing advance that any electronically controlled ignition executes as throttle input and RPM vary. But the signal from the knock sensor is not sophisticated enough to let the ECU do what you're claiming.

Go over to yotatech.com and go to the 2nd gen forum and you'll see lots of people claim that, because it's true. The ECU doesn't put the engine into limp mode due to a signal from the knock sensor, but rather because of a lack of signal from the knock sensor. (Diagnostic code 52). When ECU no longer hears from the knock sensor, it is flying blind and retards the timing (limp mode) to avoid the risk of unsupervised and possibly destructive knocking. The diagnostic message from the FSM for code 52 is "no signal from knock sensor". The normal mode of operation is for there to be a signal from the knock sensor, and for the ECU to be able to manage it by varying the ignition timing.

There is no diagnostic code for "engine knock detected so ECU switched to limp mode" in the 3vze list of diagnostics. There are only codes for a non-functional knock detector (code 52), or for non-functional knock detection capability in the ECU(code 53).

What is your source for your position on this?

Edit: Since this is a 4th gen forum, I will not comment further on the 3vze here. The OP's observations indicated that higher octane yields better mileage. I was simply corroborating his experience and explaining why it works that way. RonRJ out.

 

[CXS]

I suspect this will be one of those threads where everyone chooses to stick with their belief but I'll be reading anyway. I have the V8 and live at 5,000 ft and drive higher regularly. I usually use the cheapest available. Do I get worse mpg's because of it? I have no idea because I don't care, I drive a modified 4x4 V8 and mpg's just aren't my concern.

 

[oljedi11950]

No idea on this but I might put premium in around town driving every 5th tank just to ! But when I'm on the road love that 86 oct cheap & I drive avg 80 mph burn crap right up ! No physical evidence here just seat of pants BS .

 

[BlackWorksInc]

I suspect this will be one of those threads where everyone chooses to stick with their belief but I'll be reading anyway. I have the V8 and live at 5,000 ft and drive higher regularly. I usually use the cheapest available. Do I get worse mpg's because of it? I have no idea because I don't care, I drive a modified 4x4 V8 and mpg's just aren't my concern.

That's been my feeling about it as well. But the manual says "91 is recommended" and it does feel a bit peppier after a few tanks of 91. Been running Premium for a while now since a couple dollars won't make or break me.

Go over to yotatech.com and go to the 2nd gen forum and you'll see lots of people claim that, because it's true. The ECU doesn't put the engine into limp mode due to a signal from the knock sensor, but rather because of a lack of signal from the knock sensor. (Diagnostic code 52). When ECU no longer hears from the knock sensor, it is flying blind and retards the timing (limp mode) to avoid the risk of unsupervised and possibly destructive knocking. The diagnostic message from the FSM for code 52 is "no signal from knock sensor". The normal mode of operation is for there to be a signal from the knock sensor, and for the ECU to be able to manage it by varying the ignition timing.

There is no diagnostic code for "engine knock detected so ECU switched to limp mode" in the 3vze list of diagnostics. There are only codes for a non-functional knock detector (code 52), or for non-functional knock detection capability in the ECU(code 53).

What is your source for your position on this?

Edit: Since this is a 4th gen forum, I will not comment further on the 3vze here. The OP's observations indicated that higher octane yields better mileage. I was simply corroborating his experience and explaining why it works that way. RonRJ out.

I think the part where you two are butting heads is that you seem to imply that the 3VZ-FE's ECM is adjusting timing on a dynamic range, where as Kid is stating that it has a default value once a knock threshold has been met. I'd have to dig into TIS to really figure that out (and honestly I am a bit tired), but I don't think the older ECMs were programmed to be that dynamic in their changes.

Basically if the manual says "Premium is recommended/required" that's code for "this engine likes Premium best", otherwise don't worry about it. When it comes to the whole Premium vs. Regular thing I don't have a concrete answer anymore because of the complexities of various systems.

For example Toyota's "Atkninson's" engine in the Prius is something like 13:1 compression, but by using valve timing to bleed off pressure they produce an effective compression of something like 8 or 9:1. So basically between static and dynamic (VVTi) valve timing they are purposefully lowering compression on the engine (among other things.) So talking about compression can be come complex, not to mention how crazy VVTi timing can get/be and ignition control... I'd say most if not all our OBDII vehicles made after 2000-ish can adjust for different grades of fuel on a dynamic scale; but I doubt Premium in an engine that does not have "Premium is recommended" will do any good.

 

[Bstrom]

I've tracked fuel mileage between regular, midgrade and pure gas midgrade - a definite MPG improvement with midgrade but see little or no diff in MPG between ethanol and pure gasoline. Don't see any point in going to premium.

We have several stations selling pure gas. I'm primarily interested in long term reliability - will running pure gas contribute to that or am I dreaming? Any thoughts?

 

[RonJR]

Ethanol has 50% of the energy per gallon as straight gasoline, so you would expect that a fuel consisting of 10% ethanol would lower your mileage by 5%, all else being equal. Part of that can be offset by the higher octane rating of ethanol based fuels.

And, btw, Saab introduced an engine with knock sensor based ignition timing in 1982, so it shouldn't be surprising that Toyota would have such capability a decade or less later. Google "knock sensor based ignition timing" and do some reading if you don't want to take my word for it.

 

[yosh2000]

Gasoline sold in the US has to meet federal specifications. Branded gas simply adds their own detergent and call it something unique. The reality of it is there are less than a handful of mainstream companies that provide detergents to the suoermajors. All detergents are essentially identical.

Another fun fact is Exxon gas does not mean it came from an Exxon refinery or well. Same with BP, Shell, Chevron etc. It's all shipped on pipelines and blended at terminals. It only becomes "brand" gas when they squirt the bottle of detergent in the tanker truck. Literally.

having worked in several refineries in socal, this is all completely correct.

funny story from back in 2010 after the BP spill, every one in the area around the BP refinery was saying to boycott BP stations and go to shell stations instead. joke was on them, because BP and shell had a deal that BP would provide shell stations gas in socal because they didnt have a refinery in socal. Shell would supply BP stations gas up in norcal because BP didnt have a refinery up in norcal. being an insider and knowing where the gas really came from gave us all a chuckle!

 

[zonianbrat]

I do not think that running higher octane will make much of any difference in mpg. Biggest factor is how you use your gas pedal and where you are driving. More hills, intense city driving etc. By intense I mean that there is a difference from driving in the city of Loveland Colorado and Denver Colorado. Denver has 10 times as many lights/stop signs and in order to keep up in the faster paced city you will have to drive a little bit more aggressive like merging onto interstates/highways etc. I do believe that the top tier gasoline may be better though. I have been buying gas from King Soopers gas station since it is close and I save money with fuel points. I have lately noticed that when starting the truck it takes an extra 2 seconds to fire up and about every 15th start it took like 10 more seconds. This happened last year and I was on the forum asking you great folks what it could be. I ran a can of Chevron Techron and a couple of tanks of 91 octane top tier fuel and the problem went away. Crappy gas? Water in fuel? I can not tell. The problem did start again this past week except it is only taking the extra 2 seconds to fire up. I just put in the Chevron Techron additive and I am currently running the first tank of top tier 91 octane fuel. I'll post back some results if there are any!

I also have heard lots of people in the past talk about winter and summer blends of fuel. Anybody know if this is true? Would it affect mileage? Also what about the MAF and that fact that the air is a lot colder in winter? Sorry but now I have myself curious

 

[Bluesky 07]

It's true that there are different blends. Atlanta media covers the switch because it often affects gas prices. Don't know if it affects performance.

About engines compensating for higher octane and delivering higher performance, too bad avgas has lead because it's 100 octane. But let's pretend we could run it. Would there be an even greater performance gain? Theoretically, yes, right?

Might be smoking 'Vettes on that 5% grade. :trophy:

 

[zimm298]

I've run 87 in my 03 most of the time with no issues. Occasionally a tank of 93 and the car doesn't seem to care.

 

[nightshade000]

I've tracked fuel mileage between regular, midgrade and pure gas midgrade - a definite MPG improvement with midgrade but see little or no diff in MPG between ethanol and pure gasoline. Don't see any point in going to premium.

This has been finding as well, using a milage/gas tracking app. Our manuals recommend 91 octane, which to me, reads as our ECU's have programing that will take advantage of it if used. However, my milage tracking says the best bang for the buck with my driving has been 89 octane.

 

[07V8]

Put 93 in for the last tank.

There is a VERY noticeable difference in performance and mileage. I'll keep putting in 93 from now on.