Anyone using 15w40 synthetic? If so what brand? I haven't been able to find one in San Antonio!

 

I don't believe there is such a thing. I beleive all of the 15w40 oils are natural oil, and all the synthetics are 5w40. There are plenty of guys around here running 5W40 synthetic.

 

Mobil 1 for Diesel Trucks is a 5w-40 Synthetic. I've been running it for the past 10K.

 

Thanks for the response. I have thought about running a thinner grade but my manual shows 15w40 recommended for summer and 10w40 "acceptable" for up to 90 degrees. Nothing for 5w40. I just don't want warranty issues.

 

I use the 5W-40 year round in Mid-Mo with temps ranging from 0* to 105* and pulling up to 15,000lbs. No issues at all other than easier starts in the winter.

 

Here is the latest oil viscosity chart per TSB 05-16-6
http://www.ford-trucks.com/tsb/fullt...hp?tsb=05-16-6

 

I just ordered AMSOIL Synthetic 15W40 Heavy Duty for my '96 7.3l. My first time for synthetic so I'll let you know how it works out at a later date.

 

10w40 isn't a diesel rated grade, its a gas rated grade. 5w40 IS a diesel rated oil as is 10w30 DIESEL oil and 15w40 DIESEL oil. 10w30 is too thin for San Antonio even in winter. It just doesn't get cold enough for long enough to warrant that thin of an oil unless you travel north lots during the winter (why???--LOL). There is DAYS of reading on oil and even a whole forum section on oil and lubrication here. Good luck and happy reading.

 

RP makes a 15W40 synthetic oil that I have used for years in truck diesels, gas and diesel tractors and cars. I now use RP 20W50 year around in my X.

DSMMH

 

Hi, I was just told yesterday that if you use 5w40 synthetic in the summer you may get issues with the injector pressure, apperently the injector pressure is link somehow with the oil pressure and with 5w40 your oil pressure can be lowered, it's probably not an issue on newer trucks but mine has over 155,000 miles on it. 15w40 synthetic shouldn't give you that possible problem

 

At operating temperature there isn't a difference in 5W40 and 15W40. They are still 40W oils. The difference is in cold starts as the 5W gives you EASIER cold starts than the 15W would. Your source might not understand the multiweight oil thing.

 

Amsoil 15W-40 diesel and marine oil. With their oil filters, I've got 300,000 miles on my GMC gas truck. My 97 PSD is due an oil change this weekend.

 

Just to clarify....

A 15W-40 is a 15W oil that has viscosity improvers in it so it acts and protects like a 40 weight when at operational temps. The smaller the "spread" between the first and second number the less improvers.

A 5W-40 is a 5W oil that has more viscosity improvers in it than a 15W oil, but still is capable of providing a viscosity equal to a 40 weight oil.

In therory, a 5W-40 oil could break down to its least denominator which would be its base 5W weight which is lower than the 15W-40 which would only go down to a 15W weight. However, such an oil would have to be run for a long time and with increased sludge and "blow-by", the viscosity will thicken due to sludge... (either way, this is bad).

Using a 5W-40 year round is safe and gives the user the benefits of easier starting in any weather, but when cold it really helps and the benefits of a 40 weight viscosity when warm & hot. A synthetic oil offers better high heat protection and some (like myself) believe that it offers better turbo bearing protection when in use and upon shutdown.

Synthetics, due to the processing, are slightly cleaner and more refined than a convential oil... so I like use for this benefit as well.

Through Blackstone reports, all oils, convential and synthetics break down in viscosity in the 6.0L motor due to the use by the injectors, turbo and normal bearing lube... this motor works an oil in ways oil was never thought to be used.

Frequent oil and filter changes are key!!!!

 

Isn't this oil only CI4 rated and not CI4+????

I checked the Mobil website, and this good oil is not even CI4+ rated!!!!

http://www.mobil.com/USA-English/Mot...uck_5W-40.aspx

The "+" is for better soot and viscosity protection over the older CI4 rating.

The progression of diesel oil ratings is....

CH - Outdated rating
CH4 - Outdated rating
CI - Outdated rating
CI4 - Old, but still available
CI4+ - Old rating for convential oils and current for synthetics
CJ4 - New convential rating until Sept/Oct '07 when Shell and other synthetics upgrade to this rating.


Just curious....

 

double post