Switching to synthetic

[smitty]

I have a 99 w/ the 5.4 that I've had for three months. It has about 71000 on it and I am thinking about switching to Mobil1. We are moving across the country this week (3300 miles) and I figured it would be a good idea. I'm getting our Expy ready for the trip. I had an alignment done and transmission service done yesterday.
I've heard some people say not to switch to synthetic w/ this many miles because it could cause the seals, etc to leak.
Does anyone think I would have any problems make this switch?
Thanks in advance.

 

[seeker]

I have bought several fords used and have gone from conventional to synthetic. I even mixed it up a few times. No problems here. Just stay with a brand of oil you trust.

 

[MaverikDS]

For what it's worth I have an 01 with the 5.4 and made the switch at around 120k and have no had any issues in the last 16k.

 

[367KIX]

Every time I've seen this question asked to the experts (e.g. Road & Track magazine), the answer is the same: "no issues at all with switching back and forth between synthetic and old school oil." Synthetic is always recommended, and can be changed less frequently as well. My 97 X has never had other than synthetic and she loves it, at 217K miles, and still running strong.

 

[aircargoo]

i change my oil often cause i have acces to it... never changed thou....always 10w40 and sometimes rotelle oil for trucks..(free),lol. anyway...every month or so i do oil change with standard formula,every other time i change filter...synthitic is more expensive correct. i never look at price cause we get it by barrel at work. im guessing it must be formulated better....ill wait,mean while stick to old school oil.

 

[tonydiv]

10W40 ?? isn't that kind of thick, especially in the winter? It calls for 5W30

 

[z168]

10W40 ?? isn't that kind of thick, especially in the winter? It calls for 5W30

I went with Lubro-Moly 5W-40

 

[aircargoo]

10w 40....guess so.....doesnt ruin anything....i use mostly the ROTELLI for deisel engines. .what i didnt change yet is transmission fluid. its been in truck since i got it 2 yrs ago.....what weight in that....saw some posting...merc v.....heard in 97 was merc 3 trans oil but fluid has been reformulated.....is merc v correct fluid for 97...