My wife recently purchased a brand new 2022 Lexus NX 350 sport 2.4lL 4 cylinder turbo. The manufacturer requires premium fuel (91 octane or higher). I understand the importance of following the manufacturers requirements, but does that engine actually require premium fuel or will it run fine on regular gasoline?
It will run fine on regular gasoline. It will just lose a small amount of horsepower
Keep in mind that using regular fuel in a a car that the manufacturer specifies to use premium fuel may void your warranty if push came to shove. I wouldn't cheap out if I were you.
Check the owner's manual. Look for the words required or recommends, or something to that effect.
If it says required, then use premium.
Often times, it will say what octane rating(s) you can safely use in your car.
Since it is a Sport version, they usually require higher octane fuel. Performance versions usually require higher octane fuel. But check the owner's manual to be sure.
Premium gas has a higher anti knock index meaning it can be compressed more before it uncontrollably detonates.
Your car has a turbocharger and a high compression ratio (for a turbo) - meaning that it compresses the fuel to a higher degree than regular cars,
as such it requires fuel that has a high anti known index, aka premium fuel.
Running such a car on regular will probably be fine as most ECUs are able to get the ignition timing retarded enough to allow for poor quality fuel.
BUT in case where the engine is unable to retard the ignition enough or reduce turbo performance - your fuel will detonate and your brand new high performance engine may be toast.
Do you really want to risk damaging your engine and VOIDING your warranty over what type of fuel you put in a brand new Lexus??
It’s not worth it - just use premium.
IF it started doing that (and you would feel it), knock/ping doesn't destroy an engine instantly. You would have to drive like that for a long time. In the meantime the knock will be detected and your dash would be flashing lights at you.
Well, on turbo engines the main issue is LSPI.
From experience with Opel EcoTech and driving a Ford Dragon (also 4cyl engines with GDI/ MPI+GDI and a turbo) - you can hear it happen when you’re starting off from a standstill, usually after the 1st-2nd or 2nd-3rd shift or when applying throttle in the top gear.
No lights, Not much feel, mostly a sound and your pistons experiencing immense mechanical stress.
-
On an EcoTech A14 where the owner was told by the dealer “oh that’s a normal sound” and he did not adjust driving habits (to things like shifting at a higher rpm, downshifting before initiating an overtake, feeding the throttle slower, etc.) or use better gas - the lifespan of pistons was 25k-40k miles - then they crack/deform and the engines misfires.
-
On an engine with a much higher boost and significantly higher compression (+15%) - the force of the detonation will be higher and it may occur even further from the correct firing position - so if it occurs on a Toyota T24A it’ll probably have worse consequences.
-
Toyota seems to be trying to delay peak torque, meaning less boost, and probably a capped maximum calculated load (nothing new on turbo DI engines) - thus trying to mitigate the typical conditions that cause LSPI.
but it is an indication that they’re aware of possible issues.
-
So yeah, you can drive quite a bit with an engine experiencing detonation - but you shouldn’t.
And usually there are no lights just sounds and sometimes a vibration.
Yes, that's just technobabble language for engine knock.
If you can't hear or feel anything , and the computer isn't picking anything up, there is no "immense mechanical stress" happening. That's just grade A nonsense.
The sensors on your Opel and Ford must have been faulty.
Yet to see a car that will show a message about LSPI.
LSPI is what’s called “super knock” - a SUPER destructive version of regular knock.
On the immense pressure created by LSPI compared to knock refer to this video:
https://youtu.be/LgNf5GaR73A
-
This a video I found online of it happening on a GM SGE engine, it isn’t overly loud - but it does destroy pistons really fast.
https://youtu.be/stTSkExjFfE
Also no warning lights or messages.
(Also you see it doesn’t really affect acceleration, and it isn’t loud - on a luxury car like a Lexus - you almost won’t hear it from inside, while your pistons will crack)
-
And there’s no light that lights up when it’s doing that (this isn’t the typical knocking), you only hear it, if it’s really bad feel a vibration.