I have been lurking and reading here for a while but I finally have a question. I was wondering if anyone has experienced a break in period after switching to a full synthetic on an older engine?
When I hit 100K miles I switched my 02 Focus Zetec to 5W20 Pennzoil Platinum using FL400S filter. I did a seafoam treatment 200 miles/1 week before the oil switch using 2/3 can in the gas tank and 1/3 in the vac line. The seafoam and oil combo definitely made a difference in how the car runs (quicker starts, light tapping gone) but my MPG actually decreased by 2-3 MPG right after the oil change. After over 2K miles my MPG is going back to normal. This may be due to the super hot Texas summer and running the ac at speed 2 or higher from mid July until last week but I have never experienced a drop this much any other summer so I'm thinking the oil had something to do with it. I plan to stick with full synthetic oil only moving forward. Any thoughts?
Oil Change History -- I typically run my oil between 3500-5500 miles based on hwy use. I have used various bottled dino and blend oil and filters for DIY and the local oil change place uses bulk 5W20 blend (Kendall I think). I have also used Castrol HM 5W20 every other oil change since 70K. Only oil leaks were due to valve cover gasket but no leaks after changing gasket.
When I hit 100K miles I switched my 02 Focus Zetec to 5W20 Pennzoil Platinum using FL400S filter. I did a seafoam treatment 200 miles/1 week before the oil switch using 2/3 can in the gas tank and 1/3 in the vac line. The seafoam and oil combo definitely made a difference in how the car runs (quicker starts, light tapping gone) but my MPG actually decreased by 2-3 MPG right after the oil change. After over 2K miles my MPG is going back to normal. This may be due to the super hot Texas summer and running the ac at speed 2 or higher from mid July until last week but I have never experienced a drop this much any other summer so I'm thinking the oil had something to do with it. I plan to stick with full synthetic oil only moving forward. Any thoughts?
Oil Change History -- I typically run my oil between 3500-5500 miles based on hwy use. I have used various bottled dino and blend oil and filters for DIY and the local oil change place uses bulk 5W20 blend (Kendall I think). I have also used Castrol HM 5W20 every other oil change since 70K. Only oil leaks were due to valve cover gasket but no leaks after changing gasket.