Thanks for the replies everyone!

 

I tried it along w/ the Redline fuel conditioner in my 86 4runner 4 cylinder...couldn't tell a dang bit of difference on either. What did make a huge difference was swapping out the new cheapo $100 no-name brand 2-row core radiator for a new 3-row core $175 modine, then changing the t-stat to one w/ a lower temperature (88C to 85C). Made a huge difference. Before, the temp gauge would be above the middle without AC in 90F temps in CA. Now, I can run the AC at 111F in AZ and the needle is about 1/3 from the bottom. BTW, I use Toyota red coolant, mixed 50-50 w/ distilled water. Don't mix red & green unless you want to replace your radiator. As far as the fuel conditioner goes, I've always used Chevron 91. I changed the fuel filter at 140K mi as a precaution, but it made no difference. The chevron 91 is dang good gas! Injectors haven't been cleaned as of 193K mi...so far, so good....it just keeps going, and going...

 

I used this and purchased by the cases with my Porsche turbos. Helped immensely, especially when really pushing the cars as water cooled Porsches have very little cooling reserve and overheat easily if anything is out of spec. Of my 4 Lexus's I do/did not use it as they run pretty darn efficient to warranty this. Even my blown GS4 did not get hot in 100+ heat with a/c on.

 

We had a track run back in late 2005 up in Leon, Guanajuato and a Carrera blew out its engine and that poor little Porsche was seriously overheating (it was a hot day). I remember some people asking the guy if he used any coolant additive and when was the last time he changed it.

 

I've used it or something very similar many years ago. It was also red. It was in a Corolla. You could tell it was working as the engine ran cooler. Normally the temp gauge stays at the halfway point. But after adding it the temp was a little towards the colder side not in the middle. I don't see this as harmful. It also protects against corrosion.