1988 Sierra K1500 engine oil question ('91 350 motor)

[RayinAlaska]

(New forum member)

I purchased this older truck with a newly rebuilt 1991 350 motor (TBI). The motor has less than 6,000 miles, and the body is in beautiful shape. I have never owned a truck with such a big motor, and since this motor is very clean and purrs like a cat, I would like to take good care of it.

My question is as follows: do you see any problems if using Mobil 1 5W-30 synthetic oil instead of a heavier grade?

My reasons for wanting to use this oil is because it should help the motor with fuel consumption (less fuel usage), while still providing plenty of protection to all moving parts in the motor. I don't plan to drive this truck much, perhaps from 1,000 to 2,000 miles each year, and will change the oil once per year during the Spring.

 

[Z15]

Not a thing wrong with it, 5W-30 is the preferred viscosity.

 

[RayinAlaska]

Not a thing wrong with it, 5W-30 is the preferred viscosity.

I will go ahead and use Mobil 1 5W-30. It takes a gallon, but luckily only costs $25.00 at Walmart, which is not bad at all since it will be one oil change per year.

 

[Z15]

4 qts without filter, add more if changing filter.

 

[RayinAlaska]

4 qts without filter, add more if changing filter.

Thanks.

I just changed the oil and filter about a week ago, and it took 5 quarts. Used Penzoil 10-40 regular oil, and a NAPA filter. Today I replaced the oil only with 4 quarts of Mobil 1.

The trucks body is nice and clean, without any rust. Has a few small dings, but the paint is nice and shiny red. Will be taking it to a local shop so they replace the front axle pinion seal (in front of the driveshaft), and will ask then to also replace both right end left shafts' seals since one of them has a very small leak. Other than that there aren't any leaks in this truck. The windshield has a small crack, so I will have it replaced ($250.00 at a local shop).

I imagine that I will spend around $900.00 or so, but a couple of people have made me offers to buy it for $6K, although I only paid $4,500 for it. But I may just keep it. The truck has had some custom work done to it:

-LED lights all around
-Racing steering wheel (forgot the brand and model)
-Rebuilt engine from the ground up
-Headers plus sensor that still pass emission tests, plus 2 pipes (one at each side of the truck), each with double stainless tips
-Monster cable and fuse for installing high power receiver and amplifiers
-200-Amp alternator
-Alarm/remote door opener
-Bumper-resessed halogen fog lights
-A set of 3 red color LED (round gages) on the left column (battery, vacuum, and RPM)
-New set of tires on black spoke wheels: BFGoodrich AT LT 265/75 R16
-Supped-up suspension (no idea what shocks used)
-Towing hitch attached to frame
-The bed has a diamond-pattern aluminum step, one at each corner

I plan to take some pictures and post them here in the near future.

 

[RayinAlaska]

Decided to post the following in the case somebody else has a similar problem with an older GMC Sierra like mine:

There was a very small rain or water leaking into the cab by the passenger side. Te water was dripping right above the heater blower (or maybe right though it?). Anyway, I removed both wipers, and the air vents in front of the windshield to look for a hole or whatever was allowing for rain or water to leak into the cab near the heater blower, but could not figure what was causing this problem.

Finally after several minutes of looking around, I realized that there is a semi-oval shaped panel right above the heater blower intake, and that this panel is being held in place by a bead of a rubber or silicone material all around the edges. For some reason the right corner of this panel was not sealed properly, and rain at this point was dripping into the heater blower's intake.

I sealed it properly with black RTV silicone, and the problem is gone.