I need all info about 1990 LS 400. Like What will happen if you use 87 gas [not that I did] Prior owner did. Gas millage on the car? Why things that are in the owners manuel are not in the car? I'm so lost. Thanks for the help.

 

Have your pick, you will find about 20 threads in every forum, and maybe 50 in the maintenance forum...

https://www.clublexus.com/forums/sho...ighlight=octane
https://www.clublexus.com/forums/sho...ighlight=octane
https://www.clublexus.com/forums/sho...ighlight=octane
https://www.clublexus.com/forums/sho...ighlight=octane
https://www.clublexus.com/forums/sho...hlight=gasoline
https://www.clublexus.com/forums/sho...ighlight=octane
https://www.clublexus.com/forums/sho...ighlight=octane
http://www.toyota-4runner.org/showt...s=&threadid=683

This one has 6 links for you:
https://www.clublexus.com/forums/sho...ighlight=octane
https://www.clublexus.com/forums/sho...ighlight=octane
https://www.clublexus.com/forums/sho...ighlight=octane

Please use the search function for more info. WAY too many gas threads these days.

 

Honestly, I would treat a 1990 auto carefully. Run what it's used to running. Use one fuel brand and stick with it , if possible. Oil type and grade too.

The owners manual says premium is recommended, due to the compression rating of this V8 engine...(10.5 to 1) You engine will detonate, as you're aware, if you use regular 87.

Additionally, all automobiles included all available options in their owners manuals. This way, they print one manual supporting every option available on any new auto model the book supports.