I have about 130,000 on my 1990 inline 6 4.9.

Is it alright to use Shell Full synthetic T6 5w-40

or

Should I just stick with Shell 10w-30 conventional?

 

Are you burning oil? Do you really need the 40 wt oil? Either will run fine IMHO.

 

No I am not but looking to switch (I can get both oils at lower prices through my work) I also have quaker state and pennzoil full synthetics also.

 

I'd stick with the 10w-30.

 

I can get the Rotella T6 full synthetic for about 12.00 dollars a quart. The same price for the regular.

This is much cheaper than I am seeing so I am going to try that along with using a Motocraft filter for this oil change. I understand that the T6 has more sinc and ash which is better for flat tappet engines.

Am I correct? Please educate me anybody. I have been searching the forum but have not found anything on the RT6 in the 4.9.

 

Sure hope you mean $12 per gallon because by quart that is a terrible price.

As for protection all three Rotellas are fine for your application. The dino T, the blend T3 and the syn T6. What would the T (10W-30) cost you?

 

I have had good success using Rotella T5 [10W30 synthetic blend] and Rotella 15W40 [dino T]. Trying to reach a balance between value and quality [Zinc], I purchase the gallon size of T5 and two quarts of the 15W40. I use Motorcraft FL-1A and all are sold at our local Walmart for ~ $23.00.

 

Oops I did mean 12 dollars a gallon and I mispelled zinc as sinc too!

It will cost me a little over $10 a gallon for the 10w 30 synthetic blend. I think I will try the sythetic and see how it works.

I use the 10w 30 in my 3.8 powered buick lesabre and performs great!

 

The difference in level of zinc is insignificant. Any of them has plenty for a flat tappet engine (1000ppm or more). 5W-40 is actually not as "thick" as 15W-40 at high temperatures, due to differences in HTHS viscosity in SAE J300. So, you may get the same gas mileage as 10W-30.

 

That engine is not picky. I have the same one and year. I have tried several oils in mine with no problems. Thinner ones tend to leak a little - minor leak on drivers side of engine, but not enough to cause drips.

I used 5w40 figuring a year round since I don't drive it much (<2500 yr), but it started just as hard as 10w30. Now I have been using 5w30 year round no problems. I have 156,000 on mine. No oil usage.

 

I switched my 1986 F150 5.0 EFI from a diet of conventional oil to Rotella 5W-40 a few years back. I think it had around 120k miles on it. I'm up to 146k miles now and it created zero leaks. Oil consumption dropped DRASTICALLY and I'd swear it revved better when I switched to it from GTX 10W-30. But, this oil will clean harder than other regular oils, so expect nearly pitch black oil in the first 300-500 miles. At least that's how mine did.

 

The higher levels of dispersants in these oils darken it quickly. Folks that judge oil by how "clean" it looks are seriously mistaken. Combustion products too small to be filtered out that are not picked up by the oil have to go somewhere. This is not an issue for a new, tight engine, but ones with some miles on them.

 

2500 miles on this oil change with the T6. My truck loves this stuff it runs great! I checked it today and the oil wasn't even dark?!? It looks like it didn't even change color.

I will report back at 3500 miles when I change the oil.

 

I have put over 12,000 miles on three oil changes on T6 5w40. No leaks and gas milage is the same. I swear the truck idles and runs better.

 

Now that it is winter and you are in WI, the starting advantage of 5W full syn compared to 10W dino is probably showing up. Cold idle should be better. Three changes in six months and 12k? Why on earth are you dumping T6 that soon?