I have passed many of those speed check appaturatuses on the side of the road with my 2007 LS 460, and very consistently I am actually traveling 3 mph LESS than my speedometer in the car says I am. Eg. the roadside sign says 40, and my car speedometer says 43. Do you think this is a characteristic of Lexus vehicles in general? A characteristic of LS 460's? Or is it just MY LS 460?

 

This happens with all cars ... The problem is in the road side signs setting ,, they are calibrated on some other speedometer. try passing by those signs by another car and u will see the difference in the speed also ..

Note: The better the car, the less difference u will notice

 

I've noticed the same 3 mph difference with my Q45a. I haven't been past one of those radar signs with my LS460. However, I think those radar signs are likely to be inaccurate.

The best thing to do is find a State Police speed trap where they use Laser, which is extremely accurate. Go by at exactly 90 mph on your speedometer. When the cop stops you and asks you if you know how fast you were going, you can tell him you were hoping he could tell you!

 

^^^
LOL you are the master of driving advice!!!

As for those police speedometer display things, usually I see them fluctuating a lot.

 

hahahahhaaha, now that's a good method

 

I also have notice the speedo to be showing fast. The best way I have found to check it is with a GPS unit. There some other ways but all have shown me the speedo is off.

I wonder if there is away to have it adjusted.

As speed goes up fuel milage will drop. So I guess I could expect to take a hit there.