I would be afraid to put any kind of cleaner in the oil. If it is sludged up, it could break up big chunks of sludge and plug oil passages. I've seen this happen on an old 59 Chevy I bought for $100 back in 71. The oil drain holes in the heads were plugged and the oil level in the valve covers was above the valve guides causing oil to drain into the cylinders through the valve guides. It smoked like a coal burning train. I bought it like that to have something to tinker on and removed the valve covers and intake manifold, cleaned out the sludge and it didn't smoke afterwards. Every owners manual I've ever read does not recommend oil additives and I agree.

I would go for 5w30, something with a little higher viscosity or maybe even a 10w40.

 

This is the only safe desludging treatment, follow the directions:

https://www.auto-rx.com/

I would use the recommended grade of oil, not a full synthetic but Motorcraft synthetic blend without additives.

 

Ok thanks that's good to know. I've used seafoam in a crank case once on my Suburban and it helped with a stuck lifter noise, but I'll not bother with this and just go get some fresh oil.
I bought the truck this morning. I took the oil filler cap off and there was absolutely no air coming from the engine at all, no blow by basically, so it looks like it justs needs an oil cap which I just got at Napa for $5... Drove the thing aroundfor an hour and it's totally fine.
so again, appreciate the replies and advice and I'll keep this thread open and update on how many more miles I get out of it before it blows up!
I ended up getting it for $4200 out the door, taxes, title and fees included. So I feel like I scored a pretty fair deal there even if something big does happen.
Thanks

 

I think you did great! Good luck with it. Just additional caution, Seafoam can cause the catalytic converters to stop up.

 

Thought you may like to see the truck.. Not the most beautiful, but can't complain for the price, seems to run and drive great. Just put new tires on, put fresh 10w 40 oil and a quart of Lucas oil stabiliser and a new oil cap to stop the cap leak it had. The fresh oil and new tires have made it a new truck. It was bouncing all over the place yesterday when I was driving home, but it was the 10 ply BF Goodrich it had on it, they were rock hard. I put on some 6 ply General Grabber, slightly larger than factory original and they are running real smooth and quiet. I have noticed a very slight engine tick/knock coming from lower driver's side behind wheel... I've read a lot about this being quite normal on these coyote engines?

 

Looks like you got a good deal. Hope you get another 200k out of it!

 

10w40 is NOT the recommended grade of oil! Also, don't use Lucas in it.

 

Well Parttime, you did the exact opposite of what you should have done. Here's the issue. A worn engine like the one you bought may be just fine but the internal heat goes up with mileage. The internal heat is something you won't see on the temp gauge as the radiator takes care of it. But the internal parts are running hotter. Using a broad viscosity oil makes things even worse not to mention makes the engine run hotter internally. If you remember anything from your high school physic or chemistry class, any thin fluid will absorb and release heat faster than a thick fluid. The oil is not just a lube in the engine but also a coolant. Using the 40 oil will raise the oil temps as well as internal temps. The broad viscosity range in the heat makes for more sludge. The problem is the oil naturally can't make the spread from 10w to a 40 at temp. The blenders will use polymers to make the spread. These polymers are notorious for condensing out of formulation and making sludge. To add to that, you put Lucas in the oil. Care to guess what Lucas is? If you guessed polymers, you would be correct. That's what Lucas makes- polymers. You just added a bottle full of sludge to the already oil that's going to sludge over time. So here's what I would suggest. Run this oil no more than 2000 miles. Consider it a flush, kinda. Change it to a 10w-30 Pennzoil yellow bottle. NO additives. Use a quality filter. The Pennzoil yellow bottle has the absolute lowest NOACK which means it can tolerate more heat than any synthetic on the market and not cook off. It will go down to -25C during the winter so cold startup shouldn't be an issue unless you live in Alaska. I'd change the oil again with the same oil at 3000 miles. Most likely, with the cleaning agents in the Pennzoil yellow bottle, the engine will be reasonably clean after that. I'd suggest to continue using it until you get rid of the truck. Remember, no oil additives. Use ONLY Techron for the injection system. No other gas additives are approved by Ford and some are nothing but kerosene in the bottle. If the bottle reads "petroleum distillates" know that means kerosene. Seafoam is nothing more than a 20 viscosity light oil with some kerosene and some rubbing alcohol in it. Alcohol, better known as IPA, has ZERO business in the oil unless you just like replacing seals. Alcohols strip lubrication. The gas already has more than enough alcohol in it in the form of methanol.
Hope the truck turns out to be a winner for you. From the looks of it you can't tell it has that many miles on it. Looks like ya done good!

 

I was always under the impression that a thicker oil in the summer in a high mileage engine was better due to the hot temperatures of the day time making the oil run thinner in the engine and not coating components properly? , then put a thinner oil in right before winter for the opposite effect. Or is that not right?
The Lucas was an afterthought really. I've been using it in my high mileage Suburban for years and it makes a noticeable difference with making the engine more quiet, taking away the tappet rattles and valve noise, so I threw it in there. But I can see your point about sludging, I've not heard that before.
I will say though, it's running so much smoother now with the oil change, pretty much no engine noises at all now.
I change oil every 3000 anyway so it won't be in there long.
I'm not going to use any fuel additives either, I'll just fill up with decent petrol with the additives already inside.
Is there a good oil additive that doesn't cause sludging thatis beneficial?

 

The good oils made today already have additives. Putting additional additives in can over do a good thing. As stated before, the only additive that you should consider is Techron in the gas to help the fuel system and valves.

 

Adding Chevron Techron occasionally is a good thing. It helps keep the injectors and intake ports clean up to behind the intake valve.

 

I'd follow Labnerd's oil recommendation. He's in the business.

 

Ford recommends 5w20 that's what I've used in all my vehicles. The Motorcraft synthetic blend is a good bang for the buck. I usually go about 5k on my truck and about 6k-7k on the wife's Escape. The Escape tale 6 quarts, and wants oil changes every 7500. The truck takes 8 quarts and when I usually change it at 5k it says I have around 50% life left (not that I really trust the computer)


Your Suburban has a 5.3 I assume? The build tolerances on the 20 year old "LS" series engine is very sloppy compared to the tighter tolerances of most modern engines. That's why your Suburban seems to like the thicker oil, it helps fill the gaps in the tolerances.

I always look at the recommended viscosity and you can get an idea of build quality. Lexus/Toyota uses 0w20 on a lot of their modern engines, and they are one of the best engines in the business.

As stated earlier the Ford 5.0L "Coyote" is a very sophisticated engine. DOHC, independent variable camshaft timing etc. The passages in the Camshaft Phasers are very tiny. Neglected maintenance or wrong maintenance can cause issues because the oil passages get blocked up. Hell even the timing chain tensioner has oil pressure on it for tension strength.



Good luck! We're only trying to help you out

 

Part time, many years ago our grandfathers used a thicker oil mostly when towing. The heat that the engine would build was the novices reason for doing it. Truth is, the engines with their slop pots called carburetors were dumping gas into the engine so bad that a lot of the gas ended up in the oil. So the thinning effect was from the gas, not due to the heat. Then like all things, one guy says he used heavier oil for heat while towing and the next thing you have people using heavier oil just due to it being summer. Some of the old cars did have separate oil specs for summer and winter. Ford had a dual spec. You were supposed to use 30wt oil in the summer and 20wt in the winter. The issue was cold startup. The 6 volt batteries of the day were at task just to start the engine in the summer. Let it get cold and the starter wouldn't hardly turn the engine at all. Obviously the 5.0 has fuel injection and gas build up in the oil isn't an issue.
I imagine that 5.0 is quiet and you would be too if you had oil out of the bottle that one viscosity too thick and then had a bottle of oil thickener dumped in on top of it. That's what Lucas polymers do, they thicken the oil as the oil warms up. The hotter the oil, the thicker it becomes. I wouldn't doubt that the current oil in your engine at full temp wouldn't register as 60wt on a viscometer.

 

Ok good info thanks. I honestly never knew that, I always thought thicker oil in summer and thinner in winter. And thicker oil in high mileage engines, that's what I've always done.. So good to know and change my practices before I cause harm. Will it cause any trouble leaving the oil in for the next 2500 miles, or should I go dump it now and put it the recommended stuff?
Another issue that's popped up that you guys may be able to help with.. In very low speed, around 2-10 mph when you're driving forward, the rear end (diff I'm guessing) has a really pronounced whine or dull grind noise. It also happens when going up inclines at about 50-60 mph. I checked the diff fluid and it was full and like new, no metal filings and not dark.
Only happens when the gas pedal is pushed and you're driving, not when freewheeling, so it's not a bearing I don't think.. Any ideas?