I noticed that some Toyota and Lexus models share the same engine, but Toyota recommends regular gas while Lexus recommends premium gas. Why is that?
It’s all about the tuning. Lexus tunes their engines to advance the spark timing more than Toyota does. Premium gas is less likely to cause pre-detonation, which is important with advanced timing. You can use regular gas in a Lexus, but the engine might adjust the timing if it detects any knock, which means you’ll lose a little power.
@Kellan
Finally, someone who actually knows what they’re talking about. Everyone else is just throwing around compression without getting into the details 
Tallis said:
@Kellan
Finally, someone who actually knows what they’re talking about. Everyone else is just throwing around compression without getting into the details
Both timing and compression do matter, though.
@Fallon
Not for most Lexus and Toyota models. Very few actually change the internal components between the brands.
@Kellan
Will the ECU adjust for 87 octane in an older model like an ‘09?
viviana said:
@Kellan
Will the ECU adjust for 87 octane in an older model like an ‘09?
It should. My ‘95 SC400 handled it just fine, so I’d say yes.
viviana said:
@Kellan
Will the ECU adjust for 87 octane in an older model like an ‘09?
It should. My ‘95 SC400 handled it just fine, so I’d say yes.
I figured it would, but someone once told me the ECU couldn’t adjust in older models, and I’ve been second-guessing it since. How can I know for sure?
@viviana
I’d be really surprised if a 2000s-era ECM couldn’t retard timing. Even cars from the 80s could do it. I’ve run 87 in cars that recommend 91—like my ‘05 Acura TL and ‘17 RX450h—and never had any knocking issues. Lower gas mileage, yes, but no knocking. I wouldn’t do it regularly, but sometimes you’re stuck with only 87 octane, and it won’t harm the engine in the short term.
@Kellan
Just to add to that, higher octane burns cleaner, producing less CO2 and giving better fuel efficiency. So, with advanced timing, you could maintain horsepower while evening out the MPG you might have lost.
@Brooks
Exactly! I had a Mustang GT with an aftermarket tune, and when I adjusted it for higher octane, the ECU advanced the timing by 4 degrees. I could definitely feel the difference. When I put 87 octane in, it ran horribly and pinged a lot.
@Kellan
Is there a real advantage to advancing the spark timing and using premium fuel in a Lexus? What makes it better?
Fitz said:
@Kellan
Is there a real advantage to advancing the spark timing and using premium fuel in a Lexus? What makes it better?
More power. That’s the main benefit.
@Kellan
Accurate. Almost all modern cars have a knock sensor that helps prevent any damage.
@Kellan
I think it depends. Some engines recommend premium fuel, but others require it. For example, my RX350h uses the same engine as the RAV4 Hybrid, and premium is only recommended, not required. But my GX550, which is on order, uses a twin-turbo V6 where premium is mandatory. It’s weird because the same engine in the Tundra doesn’t require premium. Could be marketing, who knows.
@Zinn
Quick question—is my 2015 NX 200T fine with regular?
RadiantRaven said:
@Zinn
Quick question—is my 2015 NX 200T fine with regular?
If your fuel door says premium only, then stick with premium. Simple as that.
RadiantRaven said:
@Zinn
Quick question—is my 2015 NX 200T fine with regular?
Technically, it does require premium, but there’s always debate on this topic. Some say the ECU can adjust, others say it’s a scam. I personally stick with what the manufacturer recommends.
@Zinn
It’s not just about horsepower. Things like torque and gearing ratios matter too.
@Zinn
Isn’t the 5.0 V8 exclusive to Lexus?