Synthetic oil/What is the correct weight oil to use?

guido4475

Not a Member
So now I have a gasser, and am looking to do as many improvements to it as possible to get the best mpg out of it.The oil filler cap says 5w20 on it for the oil weight to be used.But wanting to try synthetic, as I am told will improve mpg's and extend oil life, do I use the same, 5w20, or go with something closer to 10w30 in sythetic?I will prefer to use Mobil One oil, as I have had excellent luck with Mobil in the past, and they have synthetic oil formulated for older, higher mileage engines.I have 130,000 miles on this 5.4 right now.Thanks in advance for any advice.
 

miguy1957

Expert Expediter
I have a 2003 GMC 6.0 gas. 520,000 I use Mobil 1 10w30 Change it every 15,000 mile , Have to add about half a Quart every 5-7000 no problems.
 

skyraider

Veteran Expediter
US Navy
So now I have a gasser, and am looking to do as many improvements to it as possible to get the best mpg out of it.The oil filler cap says 5w20 on it for the oil weight to be used.But wanting to try synthetic, as I am told will improve mpg's and extend oil life, do I use the same, 5w20, or go with something closer to 10w30 in sythetic?I will prefer to use Mobil One oil, as I have had excellent luck with Mobil in the past, and they have synthetic oil formulated for older, higher mileage engines.I have 130,000 miles on this 5.4 right now.Thanks in advance for any advice.

go to - Bob is the Oil Guy if u are driving a ford van, newer fords all require 5w20, do not change weights if it says to run 5w20, ford is real picky on that. Mileage goes down alot if u do.
 

pellgrn

Expert Expediter
I bought my 06 with a 5.4 new,so to keep ford happy i used the 5-20.I went to 10-30 mobil ful syn after the warranty was done.I have 470,000 on it and it's doing well,I had a 99 with a 5.4 that threw a rod,back then i don't think they had the 5-20 but whatever the weight was they wanted to see all my recites.That was my first expedite van and the engine blows at 32,000 miles,they changed the engine and i lost a little over a week.If you got 130,000 on it i'd do the Mobil one ful syn 10-30.I sold the 99 with around 300,000 on it,no major trouble.The guy who bought put over 500,000,i lost touch with him after that.He keep the mobil one 10-30 diet up,with a change every 10,000.
 

guido4475

Not a Member
Thank you all for the excellent advice..So since the oil cap says 5w20, then that is what I'll put in it, synthetic, and see what happens.I was thinking changing it every 8,000, with a filter change every 4,000.Although it sounds premature,I am stil not too hip on this synthetic oil thing just yet.
 

scottm4211

Veteran Expediter
Owner/Operator
I think mobil1 has synthetic with 12 and 15k guarantees. I go 8-10k with bulk oil on my gasser with no problems at 320k.
 

Turtle

Administrator
Staff member
Retired Expediter
I'd try and find out what's been being used in there already, and keep on using it. Same brand, same weight. That way the engine will continue to wear the same way, assuming there has been consistency with the oil. If just whatever was handy has been put on there, it won't matter much.
 

guido4475

Not a Member
The van was purchased from a dealer, used, so I really have no idea what was used in it before I got it.I just hope no problems develop switching.We'll see, worth a try.
 

nightcreacher

Veteran Expediter
amsoil synthetic,and their oil filter system is the best you can get.I ran a 1993 freightliner 100000 between actual oil changes.Cat had me do oil sample every month.Oil was always good,cat use to say every sample was bewtter than the previous one.I run GTX synthetic in my cars,as they only get driven short miles.Synthetic oil doesnt break down like regular oil.Oh And I ran a straight weight oil.If you want,multi weights are ok.5w40 will cover both very hot and very cold days,but the synthetic will make for easy starts in the winter time,thats why the 5w,its actually thinner.For those that swear by Lucus,the bottle says 20 %,thats 2 bottles per oil change,not one like everybody does.I quit useing Lucus,my oil samples got better,your just waisting your money.My truck at home has 980000 miles,with a cracked head,but the lower end doesnt have a problem,have used Rotella most of its life,if it werent for the cracked head,would of had no problem get over million mile on the Motor,and oil was change every 20000 miles.
Use gtx synthetic in my car did help the gas mileage,and in my Trans am it actually cut a tenth of a second off the quarter mile times.I believe in synthetic,my new truck will getting amsoil as soon as the motor gets broke in,if you put it in too soon,the rings wont seat
 

chefdennis

Veteran Expediter
I used amsoil and the filter in my carco van...started using it at 80,000 and when I gave the key to the new driver it had 368.000 miles on it and the oil was changed at 15,000 mile intervals and the filter every 10,000 for the last 100,000 miles..they came out with a new fikter for gas motors that is good for 20.000...I changed the oil and filter in the new CargoMax at 500 miles to get the Amsoil in it...changed it again at 5000 and again at 13,000, was going to go to 15,000 but I was home and it was close enough...the next change is planed for 30,000 then I go the 20,000 amsoil recommends from then on out....

I understand the apprehension of going over 8000 miles with a good synthetic, but you are really wasting your money changing it that soon....and get a good filter, and that will also go 15,000 miles with no problems....
 

aileron

Expert Expediter
Dave, if you don't mind me asking, what happened with your Ford diesel van?

Posted with my Droid EO Forum App
 

bikerpaul

Expert Expediter
I have been using Mobil 1 EP 5x20 and Amsoil 0w20 in my 2008, and have had no problems with the engine, which is at 83,000 miles. I have Mobil1 EP in all of my vehicles, with the exception of the 1997 Honda Spirit, which has Rotella 15w40. The engine did not like Mobil 1 at all. I'm told hat the reason Ford wants 5x20 instead 0f 10w30 is because the tolerances in the engine are so close, the 10w30 is to thick. I did try 10w30 once and it cut the gas mileage.
 
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Jack_Berry

Moderator Emeritus
guido, we use 5-20 in the 08 5.4. changed it every 10k usually add a qt at 7500. mechanic said to start going 15k and change all the filters at the same time. i added a qt a while ago and the oil change is due this weekend along with the tire rotation.
 
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