Switched to FS at 100K miles, break in period?

[someguy]

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.

 

[synthetic_crazy]

First of all,

to BITOG!

There is not a break-in period per se with the full synthetic. I switched my '99 Corolla at 108k and just ran a little shorter intervals for the next couple oil changes. I noticed that the synthetic cleans better than conventional, hence the shorter intervals. After running those shorter intervals you should be good to extend the mileage interval. By the way, good choice of full synthetic in your choosing Pennzoil Platinum.

 

[ZR2grizz]

Dont know if this will help, but I did the exact opposite (synthetic to dino)about a year ago with no noticeable effects.

 

[Corvette Owner]

I have switched an Accra Integral to synthetic late in life with no adverse affects.

 

[someguy]

Thanks for the welcome synthetic_crazy I'm thinking of changing the first batch around 4K. It still looks very clean on the dipstick right now after 2300 miles of use.

Now I'm thinking the drop in fuel economy was merely a coincidence since I did the oil swap in July and ran the [censored] out of the ac. I never kept MPG logs so I can't compare directly with previous years but it is pretty [censored] hot in central TX in the summer.

 

[mechtech2]

You might have messed with some sensors when seafoaming it.
And you are right, the AC use takes 2-3 MPG.

SF is basically a strong solvent - there are better in tank cleaners with modern chemistry and technology. I'd never run a solvent through an intake. Why? What do you think will happen?

I know those engines intimately, and the oil you are using was not the problem.

 

[Old Mustang Guy]

I switched my 01 Escape from MC 5W20 to PP 5W20 at 135k. The only reason I did was because when I changed the oil I realized I was out of MC so I grabbed some PP from my Mustang stash. It worked fine so I just standardized on PP. I expected a little oil use when I switched but this did not happen. I did a UOA after the second run of PP it it came out very well. Veh. has almost 160k now.

 

[someguy]

mechtech2 I didn't think of the seafoam messing anything up but I suppose its possible so that's why I mentioned it. I followed the common instructions for use in brake booster line and didn't get any CEL after use. It also gave me back some lost power and seemed to make the car run much better.