View Full Version : Anything BAD about using premium fuel when it’s not called for?
NiceGuyEddie
08-16-2021, 04:15 PM
We all know it’s a waste of money to use 91 if the manual calls for 87. I’ve found no videos or otherwise information about negative long-term effects of using premium.
Unfortunately, I have the Toyota 4.0L V6, supplied about 2005-2014 on Tacomas, FJ Cruisers, and Forerunners. It’s famous for terrible engine knock in one of three situations:
Gentle acceleration in top gear from about 1200rpm-1800rpm. (No downshift – the engine seems to struggle because it’s trying too hard.)
Climbing a gentle hill about 1200rpm-1800rpm. (Same as above.)
Full-throttle acceleration from any rpm to any other rpm (sometimes)
This engine knock problem has been all over the Toyota forums as early as 2005. Mr. Toyota said there’d be a flash-fix but it never happened.
The only way to get rid of the problem is to use 91 octane, but you can use 89 in the dead of winter (or at least a LaLa Land winter.) I have also tried 89 octane plus $2 worth of Lucas fuel additive, and this works too. (“Eliminates the need for higher octane fuel.”)
David Williamson
08-16-2021, 07:22 PM
Just costs more $$ but it sounds like this engine really needs more octane so likely better to use premium
David W
sread
08-16-2021, 07:45 PM
If the engine is knocking under the conditions stated - it needs more octane, period - doesn't matter what the owners manual says
NiceGuyEddie
08-17-2021, 09:23 AM
It really sucks - I've spoken with countless Tacoma owners over the past 12 years and the best answer I get is, "I have the same problem - I use 89 and it's not that bad."
"Not that bad?" I don't want any engine knock at all!
I'm just wondering if this could cause increased wear on any sensors, valve seals, head gaskets, catalytic converter, etc. My guess is the opposite would be true and everything would burn cleaner, but you never know.
It costs me about $400 more a year for premium fuel.
Agree with sread, your engine is telling you it needs more octane. That knocking sound is caused by detonation and here's a visual indication of detonation:
152244
We call it peppering because the black specks on the insulator look like pepper but they're actually small burnt pieces of the piston from detonation. So your $400 / year fuel up-charge is cheap insurance against $4,000 engine damage. Choose wisely.
cob427sc
08-17-2021, 12:05 PM
NAZ is right (as always) in that purchasing the premium fuel is cheap insurance. I've seen holes burned through pistons due to detonation along with scortched cylinder walls. Not the answer you want to hear but it is better than the other results. I've heard that some brands of "premium" fuels have better detergents and run cleaner, but not sure.
sread
08-17-2021, 01:04 PM
light knock at throttle tip in during cruise usually isn't a big deal, but any audible knock during full throttle and you are literally seconds away from doing major engine damage - think someone hammering the top of each piston with a large hammer and torch.
NiceGuyEddie
08-18-2021, 10:14 AM
The above comment is exactly what happens, it sounded really bad. This engine came out in 2005 so it seems to be harder to find YouTube videos about the knock.
I've been changing my spark plugs at 34,000 miles on the tick with genuine Toyota spark plugs. Every time, each spark plug looks perfect. I'm about to go on my 6th set.
I have an older-style scope/camera and the images aren't very clear but inside everything looks clean as far as I can tell.
Gas is so expensive now, so I'm thinking about switching back to the Lucas additive with every fill up.
I am using 76 gasoline. For some strange reason, I get about a 10¢ discount when I use my Amex card.
cob427sc
08-18-2021, 06:51 PM
Just curious, what state are you in and what does gas cost? I'm in Mass on Cape Cod. Premium gas, which I run in my 911 Porsche costs around $3/gallon.
As mentioned above, if your car is knocking then you need the higher octane, so can't help you there, but I can save you a few bucks.
Here in NJ regular is 87 octane and high test is 93. (Who knew octanre ratings vary by state?)
Well to make the "plus" the pump mixes about 60% regular with 40% premium. But, it is generally priced as if it were 60% premium and 40% regular.
So, my truck calls for "plus" (although it will run ok on regular because the computer retards the timing accordingly but I do notice a drop in mileage).
When I fill up, I tell the attendant (yes this in NJ land of we don't have to pump our own gas) to give me about 10 gallons of premium, then stop the pump and top off with regular. When you're filling a 33 gallon tank it saves a couple bucks. It would be even easier in LaLa land since you pump your own gas.
frankeeski
08-22-2021, 04:38 PM
I love all the "knowledge" from the rest of the nation from those who know nothing of "summer blend" fuel in CA. There is a reasonably inexpensive fix for this but Eddie won't..............
Nevermind.
NiceGuyEddie
08-23-2021, 02:28 PM
OK - with the recent high gas prices it's currently $5-$6 extra per tank, so I'm decided to use the Lucas additive full time. Buying a gallon @$23 and pouring them into the little bottles works out to less than $1 per tank.
NiceGuyEddie
09-30-2021, 04:36 PM
UPDATE - I'm sorry to say that after about a month of using 87 plus the Lucas, the engine is knocking again. It isn't even hot out anymore. I stepped up to 89 and I'll see what happens.
Dave 53
09-30-2021, 10:49 PM
As mentioned above, if your car is knocking then you need the higher octane, so can't help you there, but I can save you a few bucks.
Here in NJ regular is 87 octane and high test is 93. (Who knew octanre ratings vary by state?)
Well to make the "plus" the pump mixes about 60% regular with 40% premium. But, it is generally priced as if it were 60% premium and 40% regular.
So, my truck calls for "plus" (although it will run ok on regular because the computer retards the timing accordingly but I do notice a drop in mileage).
When I fill up, I tell the attendant (yes this in NJ land of we don't have to pump our own gas) to give me about 10 gallons of premium, then stop the pump and top off with regular. When you're filling a 33 gallon tank it saves a couple bucks. It would be even easier in LaLa land since you pump your own gas.
I work on oil tanker ships. There is no guarantee, but I can tell you it happens some times...
The octane rating on the pump is the minimum rating. Minimum - it can be higher than advertised. Some times it's cheaper for the company to make and/or ship one grade of gas than having to split production/shipments. So it's ALL the higher octane. The 89 is actually 91 and the 91 is 91.
Octane boosters is something I was looking into just earlier today to get the octane up on track days. Still trying to figure it out.
In Northern California, 91 octane is $4.99/gallon.
AC Bill
10-01-2021, 12:41 PM
Can't you just adjust the timing slightly, to avoid the pinging? Is the engine by design, not allow timing changes?
CaptB
10-01-2021, 12:57 PM
No.
Pinging is something to be avoided as it's destructive to your pistons. The best way to avoid it is using enough octane rating to prevent it. You can use higher rated gas or blend regular with premium to a ratio that works in your car but this requires experimenting and blending fuels is a hassle. If you do an internet search you'll find blend ratios of different octane rated fuels to achieve an octane rating that works for you. Weekend racers have been doing this for decades but I've never met anyone doing this on a daily driver as it's way too much work for the $$ saved.
Then there's water/meth injection that also works to prevent detonation and some of the more sophisticated systems make it easy to use. But I doubt you'll find this less expensive than just buying premium fuel for your daily driver. This is only attractive to those that need more anti-knock than premium fuel provides but don't really need race gas.
For folks looking for a miracle in a can to increase the octane rating of regular gas, do your research and especially focus on what is meant by a point of octane increase. Octane boosters all seem to rate their products effectiveness on increasing the fuel's octane rating by touting how many "points" it raises the octane rating. It takes ten points to increase 91 octane gas to 92 octane. So if the additive claims it increases your gas by 8-points that means your 91 octane pump gas is now 91.8 octane. But to most consumers, I suspect they think 8-points make 91 octane into 99 octane gas and that's almost like the old days when you could buy 100 octane at the pump (and for 25 cents a gallon).
NiceGuyEddie
10-03-2021, 03:19 PM
UPDATE - so far the 89 octane and Lucas additive has been OK. 2 tankfulls so far. It's very rare that I floor my tuck and accelerate under WOT but I've been doing it lately to see if there is any engine knock.
The spark plug change interval is 35,000 miles and I'm exactly at that. I will change them out within the next month. The plugs have always been perfectly clean when pulling them out.
In any case, the truck currently has 185,000 miles, and it's perfectly clean inside and out. The clearcoat is just showing signs of age on the hood and the left side of the driver's seat is a bit knackered from getting in and out thousands of times but that's about it. Overall I could not be happier with this truck.