Heating up engine with premium

1999 Lexus LS400. My son’s car takes forever to heat up. I stress that it does reach normal operating temperature, but you have to drive it for like 20 min to do so. We have been using regular gas to save money; it runs OK and does not ping (preignite). It is apparently retarding the timing enough to make it run OK. Anyway, I just had a thought, going back to my youth, that an engine would generate a lot less heat if the timing were retarded. It did then when I was setting these manually. So, my idea is to run premium (what it calls for) in it, during the winter to make it run hotter and warm up quicker. What do those in the know have to say about this?

Before you go thru all that, why not check if the thermostat might be stuck partially open?



If it’s retarding the timing that much, have you checked if the fuel economy is being reduced to the point where the savings are canceled out?


Retarded timing doesn’t make an engine run cool, it makes the engine completely gutless and as a result you have to give it more gas to go any given speed, which makes it burn more fuel than if the ignition was not retarded. Glowing exhaust headers are one symptom of retarded timing.
Even if the engine has to retard the timing to stave off detonation, it usually only has to do that during hard acceleration, not cruise.

I’m with Tester, check the thermostat first.

Yeah, check the thermostat. But if you’re curious, a tank of premium won’t break the bank. And check your mpgs with regular and premium, as others said you might not be saving much money.

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Read my original post again.
" I stress that it does reach normal operating temperature, but you have to drive it for like 20 min to do so. "
This is a CLUE that the thermostat is not stuck open. If it were, it would never reach normal operating temperature, especially on a cold day.
A check on mileage 2 years ago showed no difference.

If it’s partially stuck open (not wide open) it could act as you describe.


Why not just spend the extra $2.00 to fill it once with premium and find out.

There was a thread here recently IIRC where one poster said that newer Toyota engines seem to take a little longer to heat up than the older ones. So maybe its just that way by design compromises. My early 90’s Corolla engine heats up very quickly, 5 minutes or less to nice warm heat from the heater. The dash coolant temp gauge doesn’t heat up to normal operating temperature in 5 minutes though, takes a little longer than that usually. Maybe 10 minutes for that, at 35 mph.

Is the problem that the car’s heater isn’t heating the passenger compartment quickly enough after a cold start? Or are you just curious why it takes so long for the dash coolant temp gauge to reach the normal operating temperature? I don’t think your retarded timing theory would be the explanation for the latter. I’d expect retarded timing to cause the engine to heat up more quickly, at least in normal driving conditions. Sometimes dash gauges are purposely slow to react to avoid having them bounce around too much. Maybe the coolant is reaching the normal operating temperature faster than you think.

That car lists premium only, not premium recommended. You should be running premium anyway, but it’s not going to solve the heating problem.


The thermostats generally don’t get stuck, coolant leaks past the thermostat because the seal fails after 10 to 15 years.

This is a thermostat from a LS400/LS430;

Premium will not solve the engine temp problem, but if the engine isn’t operating at its optimum, if the timing is being retarded because of regular gas, it certainly can’t help.

My recommendation is to start using nothing but the recommended gas and to change the thermostat and flush the cooling system… not with a chemical flush, but with coolant. Be sure also that the plugs are good. Good plugs produce a more intense spark than plugs with gaps widened from wear.

But I find myself also wondering where you live, and what the temps drop to at night. If you’re in Minnesota or North Dakota… well, I’ll have some other suggestions. When I lived in North Dakota I had to put corrugated cardboard in front of the radiator to get the engine to warm up. The subzero air was dissipating the heat faster than the engine could produce it.

Here’s an example of a thermostat that’s partially stuck open.

I can’t tell you how many I’ve replaced because of no heat.


Oh, I forgot that part…
old T-stats that don’t close fully are not uncommon. Yours won’t be the first by a longshot. Especially at your car’s advanced age.

I had to replace the thermostat on my Corolla a few years ago b/c of too low engine temps. The problem was those concentric disks at the bottom of Nevada’s photos above were no longer concentric. One or both had warped, and I could see right through that area where they should be sealed.

Retarded ignition timing can also make an engine run hotter than normal and has a tendency to richen the air/fuel mix.

Premium gas is not going to have any effect as far as running hotter and warming up quicker.

Sounds like a bad thermostat to me.

I agree with all the posters that say the thermostat is the issue. But I would add that people used to driving a quick heating four cylinder often find V6 and V8 engines to take much longer to heat up than they are used to. My V6 Sienna always seemed to take forever to heat up but I was used to my daily driver, which was always a four cylinder.

Somewhere in the archives is a thread with a thermostat installed without the rubber seal ring resulting in slow warm up but it also failed to fully reach the normal temperature. But anyway, was the thermostat recently replaced and if so was the gasket and seal ring installed @melott?

OK, so, it not only takes 20 min to reach normal operating temperature, it is also the case that even when the engine is hot, there is no heat inside. I am guessing that I have two problems, not one.

I went back through the thread and did not see anywhere where you checked the coolant level.
Have you done so? In the radiator as well as the reservoir?

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