mikemu30

I tried mid grade and high grade one time each with ZERO change and been using 87 ever since.

BRUCELEE78

Hi All
New 19 ES350 owner. I know this topic has come up a lot as far as using regular or premium gas in your ES350, but I wanted to share a post of what I found below.
I think with the progression of engines, everyone should feel safe using regular gas in their 2019+ ES350 cars.
What do you guys think after reading below?

DEAR CAR TALK: I recently sold my 2009 Lexus ES350. It required premium unleaded gasoline (even noted on fuel cap), and I never had any problems with it. In March 2019, I bought a 2019 Lexus ES350. I was told by the salesperson that I should use regular unleaded gasoline (also noted on fuel cap). But the salesperson, and later a service adviser from Lexus, were not able to clearly explain why this new Lexus ES350 should use regular unleaded rather than premium unleaded gasoline. I am hesitant to use regular unleaded gasoline. Do I continue to use premium unleaded gasoline, or do I save money by using the regular? I enjoy reading your column every Saturday morning while I drink my cup of coffee. Thank you.
— Lucy

DEAR LUCY: You save the money. And with the money you save, you'll more than pay for every one of those Saturday morning cups of coffee, maybe even a few bran muffins. In 2009, Lexus wanted more power from the ES350's six-cylinder engine. One way to get more power is to increase what we call the engine's "compression ratio." Basically, the compression ratio measures how much pressure is created in the cylinders when the air and fuel mix is compressed.

So, the 2009 Lexus had what's called a "high-compression engine." The problem with high-compression engines is that they can cause the fuel mixture to detonate too early — before the spark fires — just due to the high pressure. That's called pre-ignition, which causes knocking and pinging that are bad for the engine.

To combat that, the manufacturer requires you to buy a high-octane fuel. The primary characteristic of high-octane fuel (other than a high-octane price) is that it has a higher ignition point. That eliminates the pre-ignition problem.
But it costs you an extra 25 cents or so a gallon. And if you drive 15,000 miles a year, that's an extra $150 in fuel costs. Or $1,500 over 10 years.

You're lucky they figured out how to make an engine in 2019 that's not only more powerful and gets better fuel economy, but also runs on less expensive fuel.

That's called progress.

Your old Lexus made 272 hp and was rated at 23 mpg overall. The new one makes 302 hp and gets 26 mpg overall. Plus, it comes with a free cup of coffee every week to help you choke down my questionable car advice.

E46CT

I use high(er) octane than regular in two instances and two instances only. If the manufacturer/owner's manual requires or recommends it.

87 (or lowest) for all else.

BRUCELEE78

So what is your car year/model and what are you using?

E46CT

it's in my sig. regular

Freds430

Good article on gasoline grades.

https://www.consumerreports.org/car-...h-extra-price/



https://www.youtube.com/watch?v=FPPkPAbzwbU&t=28s&ab_channel=CBCNews

Wilson2000

The regular vs premium debate used to be a big deal before knock-sensors, fuel injection and ECU's were invented. Nowadays, you can put regular in a vehicle that specifies premium, and the only downside is lower engine performance. You won't damage anything!

BRUCELEE78

yea but if you see my message above, I don't think there's even lower engine performance. What do you think?

LexFinally

You didn't ask me, but... I think CT summed it up. Use premium if the manufacturer says to use it.

In the case of the recent Mazda 6 Turbo, Mazda specifically listed that the car could run satisfactorily on regular, but gained over 20 hp if you used premium. In my old Acura RL, premium fuel was "required" (not "recommended"). This was because Acura advanced the timing so that the Acura version of the Honda J Series V6 would deliver more impressive-sounding numbers than the version you could buy in a Honda. Now that gasoline costs a king's ransom, drivers would probably be glad to surrrender the extra power to save the extra money, but if the engine's timing and compression ratio are set up to be unhappy with regular, that's not an option.

In a car calibrated for regular like the ES, the other posters have already said it: Nothing is gained by using premium. Now using "Top Tier" gas is another matter; whether in regular or premium octane, Top Tier gas is certified to have enough detergents to minimize the problems of finicky direct fuel injection. But octane and detergent level, again as mentioned above by others, are two different things.

Wilson2000

Depending on operating conditions, weather, i.e. air temps and pressures, speed, proper maintenance, etc., you might possibly not experience lower performance. But, that's a lot of variables, and it is exactly why engine control management was developed. That said, it's generally likely that running lower octane fuel would result in retarded timing and thus, lower performance, to some degree, noticeable or not.

Wilson2000

I hear you, but I'm sure Honda incorporated knock-sensors and the associated programming to retard the timing if someone inadvertently (or intentionally) ran lower-than-"required" octane gasoline in their Acura. I'm not suggesting anyone should, I'm simply saying it wouldn't be catastrophic if they did. In the "old days," you could blow up your engine running regular in an engine designed for high-octane!

LexFinally

There was a pretty extensive discussion of this topic on the Acurazine board. Of course, it is an Internet discussion board, so its conclusions are far from authoritative. But the opinion I found most convincing was from a poster who made the case that running the lower-than-recommended octane would eventually cause inefficient enough combustion to crap up the emissions gear downstream of the engine.

Now, I also owned a car that said "premium fuel is recommended for maximum performance." In that case, as ih the Mazda, clearly the knock sensor was there to step in and prevent badness. But I'm not so sure that was true of the Acura, although I was never the combination of daring/foolhardy/cheap required to find out.

Wilson2000

No, high octane burns slower than regular, so, it wouldn't cause "inefficient combustion." The differences in combustion rates are regulated by the timing, and all modern vehicles are programmed for this as the listed octane rating on the pump is a target/goal, not an absolute. Engine programming would also monitor any excess emissions and adjust fuel trims if needed. As stated previously, this only affects performance, and does not cause any sort of harm to the engine.

703

87 has higher sulphur content.

Wilson2000

You'll have to cite your sources on this statement. Based on my research and knowledge, 10 ppm of sulfur content is the same in both 87 and 91 octane gas, Although, there is a new 100 RON gasoline standard that reduces sulfur further.