Gs300 Engine Rpm

[DeanH]

I have a 2004 GS300 with 175,000 miles and recently have recently noticed higher rpm's traveling at freeway speeds (60-70mph). The engine is performing around 2200 rpm at 60mph which seems to be high based upon my somewhat failing memory. Can anyone verify the accuracy of this level and maybe also point me in a direction of a resource that gives factory rpm's at various speeds? Thanks for taking the time to read and respond.

Dean

[1990LS400]

Using the final drive ratio value from http://www.lexus.com/contact/pdf/2004/2004GSspecs.pdf , the 5th gear ratio value for the A650E transmission from http://en.wikipedia.org/wiki/Toyota_A_transmission and the tire circumference or radius of your tires from a website like http://www.1010tires.com/tiresizecalculator.asp , and the appropriate formula or a website calculator like the one at http://wahiduddin.net/calc/calc_speed_rpm.htm , you should be able to calculate what the engine RPM should be at any vehicle speed.

If I filled in all the fields correctly on the RPM/speed calculation form, I get 2,312 RPM at 60 mph but I'm not sure that the 1010 website gives the "loaded" tire radius. The calculated RPM is still likely close.

I used to do these calculations when I was a kid to compare the differences between the many transmission and final drive ratios that used to be optional in cars. My childhood favorite car - the 55-57 Mercedes 300 SL "gull wing" and it successor, the 300 SL roadster, could be ordered with four different final drive ratios providing top speeds ranging from 134 mph to 155 mph.

[DeanH]

So looks like I'm in the correct range Jim, thanks again.