Would synthetic oil make an older car have lower oil pressure?

I know that I have posted a million questions about my car but would synthetic oil have an impact on the engines oil pressure? Because when I switched from regular to synthetic my engine does run better and it does get better gas mileage but the oil pressure gauge on the dash is showing a lower oil pressure reading why would this be? The engine is a GM 3.1L v6 with 163,000 miles. Also the engine is not leaking oil out of the front or rear seals and I have replaced all of the gaskets on the engine when I first got the car 3 years ago. it leaks no oil at all.Would synthetic oil make an older car have lower oil pressure?
most likely when you started using better oil, it got rid of all the junk that conventional oil leaves behind. and with less restriction, the oil pressure can be a little lower. and if it runs fine, leave it aloneWould synthetic oil make an older car have lower oil pressure?
yes it does...


Synthetic oil was originally developed for high performance racing engines. Mobil tried to popularize synthetic oil for passenger vehicles back in the early 1970's. At the time, Mobil was promoting 20K or 25K oil changes with synthetic, but they soon backed down from this. Synthetic oil is a good choice if you have a vehicle with a high performance engine (in fact synthetic is required for many of these engines). It is also a good choice if your vehicle is operated in extremely cold climates. It has higher resistance to breakdown caused by heat and it flows better in extreme cold. Unfortunately for the synthetic oil industry there is virtually no advantage to using synthetic oil in a non-high performance engine that is operated in moderate climates. You probably could go a bit longer between oil changes with a synthetic, i.e. following the normal service schedule even if you fall into the severe service category, but I wouldn't advise this. In short, synthetic may give you the peace of mind of knowing that you are using an oil that is far better than necessary for your vehicle, but it won't reduce wear or extend the life of the engine. The mistake some people make it to wrongly extrapolate these benefits onto normal engines operated in mild climates, with the ultimate lack of any knowledge being manifested with statements such as ';synthetics provide 'Peace of Mind,' or 'Cheap Insurance,''; or other such nonsense.





and about filters...


Manufacturer Filters


This is usually the best choice for your vehicle.





Aftermarket Filters


These are filters made by companies like Fram,Wix, Motorcraft, Lee, AC/Delco, Bosch, Casite, Hastings, Pennzoil, Valvoline, and Purolator. The quality of these filters varies greatly. In many cases the auto manufacturer uses these filters themselves. Private label filters are made by these companies as well.





Trade Brand Filters


These are filters made for the oil change industry. They are actually no worse than the poorer quality aftermarket filters. You can't buy these at an auto parts store but you'll see them used at many of the quick oil change places.





Premium Filters


Some manufacturers of synthetic oil also make so-called synthetic filters. These are high priced and have not been proven to provide any benefit over a high quality manufacturer of aftermarket unit.
some different brands of oil filters may affect your oil pressure by as much as 20 psi
no synthetic has the same viscosity as normal oil.
If you are using a lighter weiight oil it may affect your oil pressure. If you are unsure, switch back to regular oil and see what happens.
The lower oil pressure is caused by the lower internal friction of synthetic motor oil.





With conventional oil, the molecules are irregularly shaped and sized. So when the oil has to flow through a passage the molecules have their own friction to overcome, making the oil harder to pump and therefore causing artificially high oil pressure.





With synthetic oil, the molecules are the same size and shape, because they are engineered that way, causing much less internal friction and therefore slightly lower oil pressure, but more volume of oil. This lower friction is also responsible for the cooler operation, and increased efficiency(read better fuel mileage) of engines lubricated with synthetics.





Great question, glad to hear you are having success with synthetic motor oil. I am a distributor of Amsoil synthetic lubricants. Check out some of these links for more info:





Amsoil vs. Mobil-1 and others:


http://www.amsoil.com/redirect.cgi?zo=14鈥?/a>





Browse Amsoil products:


http://www.amsoil.com/redirect.cgi?zo=14鈥?/a>





environmental benefits: http://www.amsoil.com/lit/g1059.pdf