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2004 1500 Chevy truck has low oil pressure. Will an engine flush help?

2004 1500 5.3 low oil pressure after using Lucas engine stop leak. No pressure at idle just below 40 when driving. Replace the sending unit and pressure improved for about a day. Just had a manual pressure gauge hooked up and it shows the same as cluster. No engine noise at all. I was informed that using Seafoam or another solvent could loosen up build up and cause damage. Trying to find out if using an engine flush machine may help. I am assuming that the cause of the low oil pressure is due to build up from using several qt of the stop leak over a four months. I am the only owner and I have always changed the oil according to schedule and have always used Valvoline synthetic. Please advise.

I think you may need a new oil pump. How many mile on it? The relief valve may be sticking in the oil pump. The Lucas should not plug anything up.

Try changing the oil filter.

The by-pass valve in the oil filter may be stuck wide open.


No, it won’t help. How many miles does this engine have? You may have bearings or the oil pump worn so much you can’t build oil pressure. Either is bad. Oil pumps are cheaper than a new crank and bearings.

As for Valvoline synthetic, I don’t trust Valvoline oil products after an engine builder told me some horror stories and then a buddy’s very well maintained (oil changes every 3000) car wore its bearings out at 139,000 with Valvoline. Other wise I am a synthetic “junkie”… everything including the lawnmoer.

Fore what ailment did you use the “Lucas engine stop leak”?

Seconding the idea about the oil filter. Replace it, you may get lucky.

You mention the low pressure dropped after using the stop leak. How was it before? Was it up like 40 psi at idle, or more like 12, and dropped to zero after the stop leak?

The lingering questions for me is how many miles on the truck and how is “changed the oil according to schedule” defined?

Sometimes the real world and the schedule are on different planes.

For what reason was several quarts of stop leak added to the engine oil over four months?

At any point before or during the time of adding the stop leak was the engine run low on oil?

I can’t imagine any additive actually stopping a significant oil leak.

Do you happen to know where the oil leak is located?

@mustangman Tell me more about Valvoline. I just put it in my twin cylinder lawn mower. I usually use Mobil but getting 30 wt is getting hard to find so I ended up with Valvoline. Maybe I should pull it out of there? I thought Valvoline was the better quality product?

I’ve never considered Valvoline or Havoline quality oil products. The same goes for Quaker State. I’m not of big fan of Bob the Oil Guy either. Oil is basically oil but there are differences. I used Castrol when I raced and in my daily drivers for decades with no oil related issues.

@Bing A noted race engine builder in my area refuses to warranty rebuilt engines run with Valvoline. He’s built lots of race winning engines tuned on his dyno. He’s done machine impeccable machine work for my engines and I respect his opinion.

My buddy bought his wife a car new in 1981. A 4 door, manual trans Malibu. He lived in the country so most of her driving was rural/highway. The engine wore out the rings and bearings at 139K. His father was an auto mechanic and he was a mechanical engineer. He was fanatical about changing the oil every 3000 miles using Valvoline because he thought it was the best. This buddy rebuilt the engine himself so I got to see the nice even wear for my own eyes. The machine work was done by the respected builder. We all thought 139K for a wear-out was far too early. He sold the car with the rebuilt (and hotted up with cam and carb) somewhere in the the 280,000 mile range running strong using Mobil 1.

I used multi-grade synthetic 5w40 Rotella T6 in my mower because it has lubricants for the cam. For some reason Briggs is paranoid about anything but straight weight oil. I’ve used multi-weight for years with no problems at all. My tractor always started right up when I needed to plow snow. Rotella T6 is reasonable in cost. I use Mobil 1 in any modern engine with roller tappets, though.

Many decades ago, I determined that if I used Valvoline, my car would burn oil about twice as fast. I swore off it then, and never used it since. Why do so many repair shops push Valvoline? Do they get a low wholesale price?
At one time Consumer’s posted some test results that indicated that Castrol stood up to heat without viscosity loss. So I tend to use it most of the time, with Mobil 1 0W30 in the winter.

Getting back to the original problem, I think you, OP, need to get back to us and answer some of our questions, primarily why you were dumping stop leak into the engine. Without answers, we can’t help you. The ball is now in your court. We look forward to hearing from you.

I’ll go a little off topic

It is interesting to note that these motor oil horror stories that are mentioned usually tend to have happened in the relatively distant past, and the person swore off brand x after that point

I would like to hear stories condemning brand x because of something that happened very recently, less than 10 years ago

I don’t necessarily doubt that there were substandard motor oil brands in the past

But I’d like to see proof positive that somebody bought a new car in, let’s say 2004, used brand x exclusively, and the engine was worn out in 150K, which might mean the car only lasted a few years.

And I’d like proof positive that brand x was responsible . . . over time . . . for the bad engine

I’ve used Valvoline oil in all my engines for over 45 years. Never had an engine failure and usually get over 200K miles out of the vehicles. Unless the vehicle is too rusted out to keep on the road.

Did you know that the Society of Automotive Engineers gets together with the American Petroleum Institute to set the standards on how oils should be formulated for the best performance?

As long as the container has the SAE and API certifications, the only difference between the oils is the label.


I seriously doubt that any major oil company makes an oil that doesn’t exceed every single manufacturers spec. Back in the 70’s when unleaded gas was introduced some companies (Quaker State) had a problem because of the increase in engine temps. But since then they’ve changed their formula. Use any oil you want as long as it meets or exceeds the specs of your engine and you’ll be fine.

I agree with MikeInNH, using my intellect. Emotion comes into play, though. With something as expensive as an engine rebuild at stake, many of us fall back onto our prejudices. I’ll admit to a prejudice about Valvoline based on long past experiences. My prejudice FOR synthetics comes from owning turbo cars, discussions with Mobil engineers and lots of good experience using their product.

It all comes together when one of us steps up to the parts counter to buy our oil to protect the second biggest expenditure we are likely to make. (note I didn’t say investment, cars are very rarely investments!) We go the route of lowest perceived risk.

I use Valvoline brake fluid in my Honda because it has the highest boiling point of any non-silicone DOT3 fluid. It is an excellent replacement for the Honda brake fluid.