Is it ok to use a 5w-40w synethic oil in the summer months while towing a 35ft 5th wheel trailer? I have a 2000 F350 SD crewcab 7.3 diesel. I have been using rotella 15w-40w since I bought the truck new. This winter I decided tp put rotella synethic 5w-40w in for the ease of starting in cold months. I was changing the regular oil every 3000-3500 mile. Should I do the same with the synethic? How long can you go between oil changes? THANKS FOR ALL THE HELP.

 

I have no diesel experience so take what I say with a grain of salt and a chug of beer.

First make sure that the oil weight and grade meets spec according to your manual. Not all synthetics meet spec for the Ford diesels since they use engine oil to activate the injectors and some oil don't have enough antifoam and will foam when going thru the injectors. I read this somewhere, think Trailer Life mag.

The 5W is OK since presumably you are where it is well above freezing right now so the "W" part of the oil is hybernating and only the "summer" rating is in effect. So your oil when at above freezing temps will act like 40 weight just like your 15W40. In freezing temps your oil will act like 5 weight.

With a dino the 15W is probably better since it starts with a heavier oil (15) and has VI improvers to take it to 40.

I personally like to be a bit high on the low end. What I mean is that if my manual calls for say between 0W30 and 10W40 in oil weight, I prefer to be around 5 or 10 rather than 0. This is due to my experience with 0 weights making more cold start noise, it bothers me. In summer I would possibly lean to 40 rather than 30 for better heat protection. Towing a 35 trailer is going to put strain on things so I lean to the 40 range.

But with a syn, it almost doesn't matter other than like I said, I don't care for 0W"anything" since in my expereince it makes more noise at least down to about 20F.

For your application I would go with the xW that doesn't make a lot of noise on cold start and the "summer" weight that the manual calls for. So you are probably fine with 5W40 rotella syn. I am assuming Rotella syn is a diesel grade syn and that it meets spec for Ford Diesels, you should check.

Diesels need to change oil more often than gas since their byproducts of combustion include a fair amount of acid. So you should follow your manual as a minimum. With my gas 460 that I tow a 30 foot trailer with, I use Valvoline 10W30 syn and change at the manual "normal" interval, even though I tow. I figure that is my extended drain interval. With a dino oil I would probably change more often or at the "severe" duty interval.

Hope this helps,

Jim Henderson

 

I'm using Dino 15W40 and change every 3000 miles.
Some folks go 5000 miles or more on synthetic, that's your choice.
You'll find lots of threads on here stating what people use and how long they leave it in. Just browse around and make your decision.
Read through the 7.3 forums for diesel specific.

 

I have been called 'nuts' by a lot of people regarding my oil change intervals using Amsoil Synthetics.

In my gas engine I go for the 25K mile oil changes. Every 12.5K miles I change the oil filter and send the oil to the lab for testing. I have a '92 sable with over 236K miles on it that has always been changed this way.

In my diesel I go for the 15K oil change. I change the oil filter every 7.5K miles and send the oil to the lab for testing.

Amsoil rates the oil I am using for those intervals. The deciding factor for me is the oil lab tests. Diesels are more demanding on oil than the gas.

 

Go AMSOIL!!!....I'm a AMsoil hardliner and it's too bad that everyone else doesn't get it...also use the bypass system so I NEVER change...only test and add.....

 

Are either of you two an Amsoil dealer, preferred customer or wholesale buyer?

 

Mobil Delvac 1 10W40 is diesel and Power Stroke rated.
Still change it at 3000 miles. Way to much soot and acid that needs to be out of the engine.
Motors cost to much money, oil is cheap, even synthetic is cheap.

 

i have the same ?, some one care to answer it.

 

Don't get dave fired up about scamsoil...lol

 

ok lets just end it. each to his or her own brand

 

Nope. Just a personal user. However, I do have a friend that is a dealer and I purchase from him at hist cost.

 

Most extended service Amsoil products ARE NOT API certified, a requirement of most vehicle manufacturers for the warranty to stay valid. Here is a list
of Amsoil products that are API certified:

http://eolcs.api.org/DisplayLicenseI...LicenseNo=0995

Bottom line, you can buy API certified products, that are a lot cheaper than Amsoil products, this is how a MLM company works!!

 

bob that whole web site is full of great information. thank you.
but sorry guys this thread caused some very hot problems last night. please take note of that very good link and web site bob posted as i,m putting this one to sleep.
nothing against any one. this subject company is known to cause problems. and i do not want to have to redeal with it.
again nothing is against any one. we all have our personal choice, so each to his/her own

 

Well put Charlie...............and thanks Bob