Does Thicker Oil Increase Oil Pressure?

In this video we answer a very common question about using thicker oil to help an older engine with low oil pressure.

[lordofwar]

I think you should consider teaching this stuff professionally at a trade school when you get older and don’t feel like working on engines anymore. You explain everything really well, you’d be a natural.

[tectalabyss]

part 2 As oil is forced between a bearing and journal, many polymers have a tendency to align with each other, somewhat like nesting spoons. When this happens, viscosity drops. Then when the oil progresses through the bearing, the polymer molecules entangle again and viscosity returns to normal. This phenomenon is referred to as temporary shear.

Because the Sequence VI-B test responds to reductions in viscosity, oil formulators rely on polymer shear to pass the test. A shear stable polymer makes passing the GF-3 fuel economy test much more challenging.

New rules defining the cold-flow requirements of SAE viscosity grades (SAE J300) became effective in June 2001. The auto manufacturers were afraid that modern injection systems might allow the engine to start at temperatures lower than the oil could flow into the oil pump. Consequently, the new rules had a thinning effect on oil.

The auto manufacturers now recommend thinner oils for their vehicles than in the past. Years ago, SAE 10W-40 was the most commonly recommended viscosity grade, later migrating to SAE 10W-30. SAE 5W-30 is most popular now, but Ford and Honda recommend SAE 5W-20. It is likely that more widespread adoption of SAE 5W-20 and other thin oils may occur to help comply with CAFE requirements.

Because of the change in cold-flow requirements and the fuel economy test pushing formulators toward the bottom of the viscosity grade, today’s SAE 10W-30 oils are more like yesterday’s (GF-1 spec) SAE 5W-30 oils. On top of that, there is a trend toward auto manufacturers recommending thinner grades. This seems ridiculous. SUVs and trucks, with their inherently less-efficient four-wheel drive and brick-wall aerodynamics, need powerful, gas-guzzling engines to move their mass around in a hurry. In response, auto manufacturers recommend using thin oils to save fuel. Incredible!
Viscosity and Wear

Thinner oils have less drag, and therefore less friction and wear. Right? Perhaps in the test engine or engines that experience normal operation. But somewhat thicker oils may offer more protection for more severe operations such as driving through mountains, pulling a boat, dusty conditions, short trips, high rpm, overloading, overheating and overcooling.


Figure 2. Ring Wear

Any abrasive particles equal to or larger than the oil film thickness will cause wear. Filters are necessary to keep contaminants small. The other side of the equation is oil film thickness. Thicker oil films can accommodate larger contaminants.

Temperature has a big effect on viscosity and film thickness. As a point of reference, one SAE grade increase in viscosity is necessary to overcome the influence of a 20°F increase in engine temperature. At a given reference point, there is approximately a 20°F. difference between viscosity grades SAE 30, 40 and 50. SAE 20 is somewhat closer to 30 than the other jumps, because SAE 30 must be 30°F higher than SAE 20 to be roughly the equivalent viscosity.

In other words, an SAE 20 at 190°F is about the same kinematic viscosity as an SAE 30 at 220°F, which is about the same viscosity as an SAE 40 at 240°F. This approximation works well in the 190°F to 260°F temperature range. One might be surprised at the slight amount of difference between straight viscosity vs. multiviscosity oils with the same back number (for example, SAE 30, SAE 5W-30, and SAE 10W-30).

If an SAE 50 oil at 260°F is as thin as an SAE 20 oil at 190°F, imagine how thin the oil film becomes when you are using an SAE 5W-20 and your engine overheats. When an engine overheats, the oil film becomes dangerously thin and can rupture.

[johnvlahidis_google]

In Greece, engineers often change the viscosity to thicker, especially in scooters, when they see that the manufacturer recommends, for example, 5W-40. They don't like this number and put in 15W-50, resulting in engines being destroyed without cause. Then they curse and blame the companies, saying that they not manufacture more durable engines like old times than they do today. In no job do they ever read what the manufacturer recommends because they believe they know better than anyone else.

They do the same when an car engine burns oil. Instead of fixing the problem, they change to a thicker viscosity oil, resulting in accelerating wear exponentially.

thanks for video i share to my dump meccanic friends

[johnfranklin]

Southern California here. Ive been using 20 50 in my 58 Cadillac and 68 Mustang for about 40 years now. No problems engines run fine, sound healthy.

[morebeer]

In most worn vehicles that have low pressure due to bearing wear, it's the second, or "operating temp" number you want to increase to compensate, BUT only incrementally. You never want to change the recommended first number, or the "W/cold crank" number, of your viscosity. It's usually okay to go from a 5W-20 to a 5W-30, or a 5W-30 to a 5W-40, but you would likely do great damage, as he described, if you jumped levels of viscosity and went for example, from a 5W-30 to a 20W-50. This is especially true for modern VVT engines.

[markcrowell]

Great video- love how he immediately opens the video with the answer to the exact question that was being asked.. 👍🏼👍🏼
Then immediately said it was a horrible idea.
Within 10 seconds I had the answer and knew not to do it.. I HATE watching long videos to get to an answer.. thx bro - keep the videos coming! I’m subscribing

[johnnytsunami]

It really depends there is too many variables to say thicker is a bad idea. I ran my avalanche with 5w30 for 200 thousand miles and it had a loss of oil pressure due to bearing clearance and wear over time once I added 10w40 it runs better has oil pressure back to normal and makes less engine noise. I’m no professional but thicker in my case has fixed my small issues. I now have 240 thousand miles and still use the 10w40 with zero issues and better performance it runs like new again

[catapult]

I purchased a 1998 Nissan frontier brand new at the time less than 3 miles on the odometer. For the first six months ownership I use the recommended weight viscosity oil, 5W 20. Every time I started that engine up it clattered made all kinds of noise until oil pressure was built up, after my warranty was gone, I put in 10 W-30. The start up clacking stopped and I put well over 300, 000 miles on that engine with no issues.

[pete]

I parted ways with the " thicker oil is better" crowd years ago. In my 40 years as a mechanic, I've never once seen an engine hurt from the oil viscosity being what the manufacturer recommended. OTOH, Ive seen quite a few damaged by the " thicker oil is better" crowd who think theyre smarter than the engineers who designed both the engines and the oil for them.

[tectalabyss]

Part 4 final. Although thinner oils with less antiwear additive outperform more robust products in the 96-hour fuel economy test, it is not clear that such products save fuel over the useful life of the engine.

Every fluid is a compromise. Oils recommended by the auto manufacturers seem to compromise protection from wear under severe conditions to gain fuel economy and catalyst durability. It is important to recognize that to use a product that offers more protection from wear will most likely compromise your warranty. Thicker oils also compromise cold temperature flow, which may be of concern depending upon climate and season.

The best protection against wear is probably a product that is a little thicker (such as SAE 10W-30 or 15W-40) and has more antiwear additives than the oils that support the warranty. The best oil for your vehicle depends on your driving habits, the age of your engine and the climate you drive in, but it is not necessarily the type of oil specified in the owner’s manual or stamped on the dipstick.

[razaghumman]

Thanks man good info, I switched to 10w30 heavy duty 100% synthetic AMSOIL from 15w40 mobile delvec, improved mpg and engine sounds n run better, have a 2013 Volvo vnl with d13 750, 000 miles nothing is been touched on my engine so far,

[brycebrandon]

I am a truck driver who just subscribed to your channel, I am currently saving money to buy a KW W900, I want a CAT engine and I want to do most of the maintenance myself, maybe not at first but eventually I plan on moving to Wyoming with my family and buying a house with land. I've seen plenty of properties that have garage facilities that are big enough for a truck. I really appreciate that you are strictly CAT as I am also a fan of CAT. I hope to learn a lot from your channel.

[Jessestravels]

I have a 3v 6.8 v10. In a ford. I had cam failure with follower issue. Wount up needing to replace both cams lifters followers. High volume pump and replaced tensioners. Had a tap after complete, was a light tap. Dropped pan. Replaced rod bearings and polished crank surfaces best i could using some old school tricks. Tap went away. Factory calls for 5w20. Have been using 5w30 in winter and 10w30 in summer with stp oil stabilizer. Have over 50k on the repair. Cam Journals showed wear when the cams were replaced. They are non serviceable so I just threw the new cams in. I think with engine wear you have increased tolerances that can handle thicker oil. It's not ideal but it works. A stronger pump probably helps. Every situation is different. I left the crank bearings in but pulled a cap to see the wear and it wasn't good. Thought about rolling new ones in but the grooves in the crank could've eaten the new bearings. No room for polishing on the crank journals. Most wouldn't have attempted this so there is a real world experience.

[JT-qfit]

You are absolutely spot on. I can't count the number of times Ive seen this done to high mileage engines.

[AutodidactEngineer]

What I did is I replaced my MF 135 mechanical oil pump with an electric oil pump.
Also I reamed out all the oil passages throughout the engine compartment, I also installed aftermarket under piston oil sprinklers and now I installed an oil pressure nob that goes from 12 PSI to1.2 bar, also the cool thing is that when I want to start up my tractor cold, I turn on the oil pump for about 20 seconds then crank the engine.
The pump I am using is used in industri SCANIA trucks.

[johnnylightning]

Yep that's the right but I'm sure there will still be folks that argue with you. One thing you didn't touch on is that more freely flowing oil take heat away from components more quickly. Every motor is oil cooled to a certain extent, air cooled engines almost exclusively so flow is important to keep cool oil coming in and pushing the hot oil out. Keep the good stuff coming.

[morgansword]

When we were kids in the sixties and seventies, we didn't know any better and more by luck than by know/learning, I was broke and having kids means feeding them first. So when my oil pressure made a dramatic drop, I had oil, thirty weight but I didn't have money to grab some ninety weight and add to it. I had to work and that meant drive on at any cost.... I was very lucky as money, parts and time all came at same time as I tore it down to put which ever bearing it needed, not a set mind you but just ones needed. I pulled it out and pulled pan and timing cover and all the top off.... seen my timing chain was bad bad. I take the rockers loose, and pulled that cam that had a pressed cam gear out and looked back in the holes to see brass. lots of it and thinking bottom would be gone, took one to look and see how scared it was to find that sure it had miles but it was way usable. Going further and not losing their places, now being careful, I looked at the rest of them and conquered the bottom could still roll on if I had pressure. All kids have spare parts if they run same brand, etc and so grabbing another block that had a good cam knowing it was good but bottom was shy, I swapped my good crank and bearings in and kept bearings for good crank (one just pulled out) and swapped the mains with the crank and used the rods on the pistons in the one who was going to live again so the journals kept same same but just different pistons as it to me was a fifty fifty thing. New gaskets where I had them, pan, the timing chain was still good in the donor so just kept those gear and chain sets together. Next morning, I fired her up and seen the gauge jump up and what a difference having a good t chain can make any way. I actually ran that engine for a year being kind and not racing. It got pulled for a big bad motor and the limper was put under the bench for crap to fall on for a few years and when cleaning out garage, brother comes by and asked if I had a builder and I pointed at "limper" and said ran when pulled and will go to dump unless you take it. He takes it home, power washes, gaskets, cheap bearing set without micing or checking. He ran perfect circle rings in everything and he never even cleaned the junk out of the ring glands, just rings and bearings, t chain, seals with same heads no valve lap or other.... It ran great but perfect circle rings were soft and it needed rings again soon and then just got scraped. He drove hard and fast and should of been charged for engine abuse.

[markm]

Very nice. I learned exactly what’s going on and got it in the first shot.

[thetowndrunk]

2 things have changed a lot over the past 20 years- oil quality, and engine tolerance (especially with the newer emissions systems). Oils are far more advanced now, than even in the 90’s. A straight up conventional does a fantastic job at protecting engine parts, and takes much longer to degrade than it used to. Synthetics now are absolutely amazing. I personally am not a fan of extended drain intervals, but there are many instances semi engines going 1 mil+ without an oil change, using synthetics, bypass filters and consistent oil analysis. As far as engines, they’re not only built to much more precise tolerances than years ago, but material technology means those components wear at a slower rate on average. So, in my totally public educated opinion- stick with the manufacturers suggestion on oil weight, and avoid the snake oils. First off, that stuff that resembles boiled down honey has no additives in it, so you’re actually diluting the additive package in the amazing oils available. As for the ideas about gear oil- yes, technically a lot of them have additives in them, so you’re not necessarily diluting the additive package of the oil, but consider what that oil is made for, which is gearing, and think “hm, would they use the same additives for gearing as they would for an engine? 🤔”- I’m going with probably not. Worst of all, because tolerances are so tight, that oil is gonna have issues flowing in a modern engine, and you’re thereby increasing wear, which is the very thing you were trying to fight by adding the goop. Yes, it’s true that manufacturers have been using thinner oils for CAFE purposes, but those engineers didn’t just take fuel efficiency into account. They also took engine wear into account, and had to find the best balance between those 2 goals. As for diesels, well, the overwhelming majority still call for the same 15W40 we were using in the Stone Age, so not a ton of guess work needed there. My advice- put the recommended oil in, change it regularly, avoid the snake oils and old school advice (at least if it’s a modern engine), and focus on your driving habits. That’ll make the biggest difference in longevity.

[ghettygram]

Speed up 1.5 👌 exactly what I was looking for. Thank you