Well I have been running the car with 7 full quarts of oil for the past couple weeks and it seems like the cats are working overtime when the car has been driven pretty hard. Should I go change my oil and only fill the car with 6.0-6.5 quarts? The dipstick reads right at full with the 7 quarts. With 6.5 the dipstick reads low... There is no oil blowby or oil consumption. I am using Mobil 1 5w-30 with a Motorcraft oil filter. Any suggestions please