i changed my oil today i went with mobile 1 fully synthetic performance driving formula. before i changed the oil the oil pressure going down the highway was always around 40 lbs. with valvoline. now after the oil change its at 50-55. did any of you notice this or is this normal with the synthetic. that was my first question. the second is this- i just started running 92 octane in my car i always ran 89 ethanol and my car starts better i get better gas mileage but the exceleration is terrible i had better exceleration with the 89. why is this?