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Originally Posted by Pantera99
Hi all, just my $.02. Have always been a Mobil1 and Amsoil user. Was intrigued by all the hype with Royal Purple so I changed to that at 15,000 mi. Now I have 17,500 on her and if anything my mileage went down and no it's not from hammerin it because of the performance gain Royal Purple claims. I also switched to a K&N air filter, mileage went from 15-15.5 down to 14 or under 14. I find it had to believe any synthetic could get worse mileage than dino oil.
Any thoughts? Back to Mobil1 next change. Always good results with Mobil1 in my '02 Xterra.
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I religiously change oil every 1500-2000 miles and have used Pennzoil or Castrol or even Chevron 5W-30 (6 qts) + Marvel oil (1 qt); oil filter is regular Fram (whatever is on sale). Since I change oil & filter quite often, I figured that dino oil is fine. I just want the engine clean since it's my daily driver (avg 70 miles/day; hwy & city). On my last oil change, however, I finally tried the Mobil Synthetic 5W-30 (7 qts). I didn't add the usual 1 qt of Marvel Oil - not sure how synthetic oil will react to it. Noticed right away that my truck's gas consumption plummeted from 350 to @305 per full tank! Now I'm, wondering: Is it because it's Winter? Or the omitted 1 qt of Marvel oil? Or the 10% ethanol? Or the synthetic oil itself?