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Discussion Starter · #1 · (Edited)
I heard 5W-30 might reduce milage by 1-2 mpg since its higher viscosity at higher temperature. Will 0W-20 improve mileage? I don't believe it will as it has same viscosity as 5W-20 at high temperature. I am thinking of using 0W-20 since it's readily available at Costco stores but 5W-20 has to be mail ordered which adds 10% to the cost.
 

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I use 5w-30 high mileage. It seems to work better at controlling oil use and warmup noises. I rarely if ever get much below freezing and store the car in an attached garage.

Is your motor worth the few dollars you save?

Let is know what you find.
 

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I have played with weights in other cars with no noticeable impact. If an engine that calls for 5W-20 has problems due to being serviced with 0W-20 or 5W-30, that engine already had problems. Engines are designed to work in pretty harsh conditions like extreme temperature that will cause viscosity of the oil to be outside of the "normal" range and the engines can tolerate this without issue. Handling the slight viscosity change you are talking about is well within the capability of any halfway decent modern engine design. It is also worth noting that many engines allow for various weights of oil right in the service manual. For example, Skyactiv:

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I have played with weights in other cars with no noticeable impact. If an engine that calls for 5W-20 has problems due to being serviced with 0W-20 or 5W-30, that engine already had problems.
Like high mileage?
Engines are designed to work in pretty harsh conditions like extreme temperature that will cause viscosity of the oil to be outside of the "normal" range and the engines can tolerate this without issue. Handling the slight viscosity change you are talking about is well within the capability of any halfway decent modern engine design. It is also worth noting that many engines allow for various weights of oil right in the service manual. For example, Skyactiv:
I wonder how this applies to a 17 year old engine with 200,000miles.
I just think back to making a change in my Corolla to a lighter weight oil at around 220,000 miles and at the end of that oil interval getting about a teaspoon of metal on the bottom of the drain pan. It ran another 80,000 miles but really did not sound good revving beyond 4,000RPM after that. 🤷‍♂️

By the way, is that Road Atlanta as your avatar?
 

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Discussion Starter · #5 · (Edited)
Like high mileage?
I wonder how this applies to a 17 year old engine with 200,000miles.
I just think back to making a change in my Corolla to a lighter weight oil at around 220,000 miles and at the end of that oil interval getting about a teaspoon of metal on the bottom of the drain pan. It ran another 80,000 miles but really did not sound good revving beyond 4,000RPM after that. 🤷‍♂️

By the way, is that Road Atlanta as your avatar?
I am going to try 0W20 full synthetic and do oil changes myself. I have been the shops put conventional 5W20 in recent years since they charge a lot more for full synthetic. My car is 18 years old with 107K miles.
 

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Like high mileage?
I wonder how this applies to a 17 year old engine with 200,000miles.
I just think back to making a change in my Corolla to a lighter weight oil at around 220,000 miles and at the end of that oil interval getting about a teaspoon of metal on the bottom of the drain pan. It ran another 80,000 miles but really did not sound good revving beyond 4,000RPM after that. 🤷‍♂️

By the way, is that Road Atlanta as your avatar?
I would not consider high mileage an issue and I don't think the manufacturer would either, unless there was some serious neglect along the way. I don't own a car with less than 200k on the clock and haven't in years. The oil weight changes I have made have been on these high mile engines. What kind of weight change did you make on a Corolla engine that yielded you metal chips?

It is! I actually signed up for the board to learn and share some of the changes I am making to my 6 before I take her for a track day there, probably in December.
 
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I would not consider high mileage an issue and I don't think the manufacturer would either, unless there was some serious neglect along the way. I don't own a car with less than 200k on the clock and haven't in years. The oil weight changes I have made have been on these high mile engines. What kind of weight change did you make on a Corolla engine that yielded you metal chips?

It is! I actually signed up for the board to learn and share some of the changes I am making to my 6 before I take her for a track day there, probably in December.
Nice. My old home track is Laguna Seca but up here in the PNW we have the baby track at PIR.

In all fairness it was a switch from 10-40 conventional to 10-30 full synthetic. It was a pretty fast run from Seattle to Portland with a trio of cars that were substantially out of my class.
 

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Discussion Starter · #8 ·
Nice. My old home track is Laguna Seca but up here in the PNW we have the baby track at PIR.

In all fairness it was a switch from 10-40 conventional to 10-30 full synthetic. It was a pretty fast run from Seattle to Portland with a trio of cars that were substantially out of my class.
10-40 to 10-30 switch means going to thinner oil when engine is warm. 5-20 to 0-20 means no change in oil viscosity when engine is warm so I think its less risky. 0-20 and 5-20 should be exactly the same in PNW weather. Last time I checked with Costco they had 0-20 in all the warehouses in PNW but 5-20 was only in Anchorage, Alaska store :)
 

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The basic rules for oil:

1. The higher viscosity number on a multi-weight should not be decreased below the manufacturer's recommendations for the temperature range in which you are running the engine. That is the "hot" number and is important for clearances; exceed the film strength on that and very bad things happen wear-wise very fast.

2. The lower viscosity number on a multi-weight CAN be decreased but should NOT be increased above the manufacturer's recommendation for the temperature range in which you are running the engine. Decreasing it will improve cold-start flow; increasing it DAMAGES cold-start flow. Most engine wear occurs on cold start. Shouldn't be hard to figure out there.

3. The kicker: The WIDER the range on a non-synthetic the more subject to shear of the VIs in the oil is and the faster it loses its higher end rating. This means that increasing the range between the lower and upper numbers on a non-fully-synthetic oil is bad and thus should never be done without support of oil analysis starting at 1/2 the recommended OCI and working upward to the full interval. If you break that rule and the VIs shear down your 10w40 now has the film strength of a 10 weight oil at high temperature instead of a 40 and you will likely get wildly-accelerated wear or even spin a bearing. This is the limiting factor on the above and usually precludes making a change from recommendations. This does not generally apply to full synthetics as they do not use VIs, or much of them anyway, to achieve their ratings provided the manufacturer did not require fully-synthetic oil in the first place. If they did, and many manufacturers have done for quite a while, then that was taken into account.

4. Never run a non-synthetic oil in an engine where full-synthetic is recommended or required. The reason for the recommendation or requirement is that as emissions standards have tightened the top compression ring to fire-deck distance has decreased. This causes the temperature at that ring land to increase substantially, and if the manufacturer has determined that dino-based oil cannot withstand it they recommend or require full-synthetic oil. Violate that recommendation and you are at severe risk of oil coking which will stick piston rings (especially the top one), sludge up your engine or both; this is how you wind up with severe cylinder damage or oil circulation problems inside of 100,000 miles. If you've ever seen an engine with all kinds of sludge under the valve cover this is why it happened. In severe cases it either sticks a piston ring and scores the bejeezus out of a cylinder wall or plugs up the oil pickup screen, the engine loses oil pressure and is destroyed.
 

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Discussion Starter · #10 ·
The basic rules for oil:

1. The higher viscosity number on a multi-weight should not be decreased below the manufacturer's recommendations for the temperature range in which you are running the engine. That is the "hot" number and is important for clearances; exceed the film strength on that and very bad things happen wear-wise very fast.

2. The lower viscosity number on a multi-weight CAN be decreased but should NOT be increased above the manufacturer's recommendation for the temperature range in which you are running the engine. Decreasing it will improve cold-start flow; increasing it DAMAGES cold-start flow. Most engine wear occurs on cold start. Shouldn't be hard to figure out there.

3. The kicker: The WIDER the range on a non-synthetic the more subject to shear of the VIs in the oil is and the faster it loses its higher end rating. This means that increasing the range between the lower and upper numbers on a non-fully-synthetic oil is bad and thus should never be done without support of oil analysis starting at 1/2 the recommended OCI and working upward to the full interval. If you break that rule and the VIs shear down your 10w40 now has the film strength of a 10 weight oil at high temperature instead of a 40 and you will likely get wildly-accelerated wear or even spin a bearing. This is the limiting factor on the above and usually precludes making a change from recommendations. This does not generally apply to full synthetics as they do not use VIs, or much of them anyway, to achieve their ratings provided the manufacturer did not require fully-synthetic oil in the first place. If they did, and many manufacturers have done for quite a while, then that was taken into account.

4. Never run a non-synthetic oil in an engine where full-synthetic is recommended or required. The reason for the recommendation or requirement is that as emissions standards have tightened the top compression ring to fire-deck distance has decreased. This causes the temperature at that ring land to increase substantially, and if the manufacturer has determined that dino-based oil cannot withstand it they recommend or require full-synthetic oil. Violate that recommendation and you are at severe risk of oil coking which will stick piston rings (especially the top one), sludge up your engine or both; this is how you wind up with severe cylinder damage or oil circulation problems inside of 100,000 miles. If you've ever seen an engine with all kinds of sludge under the valve cover this is why it happened. In severe cases it either sticks a piston ring and scores the bejeezus out of a cylinder wall or plugs up the oil pickup screen, the engine loses oil pressure and is destroyed.
Based on this, Full synthetic 0-20 is actually better for the engine than Conventional 5-20. Given that you can buy 10 quarts for FS 0-20 for $29.99 + tax at Costco, DIY oil change with it is cheaper than an outsourced oil change with conventional 5-20.
 

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Based on this, Full synthetic 0-20 is actually better for the engine than Conventional 5-20.
Correct. The full-synthetic 0w20 does not have the VI shearing problem (there ARE no dino-based 0w20s I'm aware of) that would make it ill-advised to use a blend or dino-based wider-viscosity spread, so if 5w20 conventional is specified as acceptable then a full-synthetic 0w20 should be modestly superior in cold-start protection and give up nothing on the hot end. Being fully-synthetic it likely will be superior across the board.

Do not extend drain intervals, however, without solid OCI support. While dino-based oils lose their VIs over time and thus go out of viscosity range (to the lower end, which is bad!) what usually kills a full synthetic is additive package exhaustion, fuel dilution and similar, which are still in play irrespective of the base stock.
 

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It is! I actually signed up for the board to learn and share some of the changes I am making to my 6 before I take her for a track day there, probably in December.
Nice, I'm also in your neck of the woods. I'd love to do Road Atlanta at some point but it kind of scares me for some reason. The only wheel-to-wheel racing I've done is Champcar at Sebring a few years ago.
 

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Nice, I'm also in your neck of the woods. I'd love to do Road Atlanta at some point but it kind of scares me for some reason. The only wheel-to-wheel racing I've done is Champcar at Sebring a few years ago.
Very cool, some variety of inexpensive endurance racing is on my bucket list for sure!

I am just doing an HPDE so nothing too crazy on the competitiveness and intensity. I realized a couple of months back that I have been wanting to get out on RA for a decade now and kept putting it off. I figured it was probably time to do it lol.
 
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Very cool, some variety of inexpensive endurance racing is on my bucket list for sure!

I am just doing an HPDE so nothing too crazy on the competitiveness and intensity. I realized a couple of months back that I have been wanting to get out on RA for a decade now and kept putting it off. I figured it was probably time to do it lol.
I did a driving course at Road Atlanta several decades ago. You'll have a great time and should learn a lot, or reinforce good habits. Getting your personal car on the course (if they still do that) was a blast.
 
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