My 1988 300SEL. There is the meter with the numbers that range from 0 1 2 3. When it’s on idle the needle is on 3, but when I engage on R or D the needle drops to less than 2. And when I am on the highway (high acceleration) the needle will then go back to just about 3. What does this mean. I recently moved from Texas to Toronto, I am not sure if this has to do with anything. Thanks.