Why not multigrade in lawnmower?

Page 2 of 2  

Bennett Price wrote:

I wouldn't second guess the advice of the maufacturer. And unless there is evidence, I wouldn't assume or jump to the conclusion that price of the oil has anything to do with it.
For example, for my boat, Mercruiser lists straight 40W for their V8 marine engines, with no off the shelf multi-grade recommended. Now it's hard for me to believe they are doing that based on oil cost, since in marine applications, the cost of oil is trivial.
And it's not true that mulit-grade is not used in lawn mowers. My Honda takes 10-30.
I would use the recommended oil and make sure it's changed at least the recommended hours or once a season.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@optonline.net wrote:

You might consider synthetics as being a single grade oil. And synthetics are much better at standing the high temperatures you find in air cooled engines. It just happens that it does not get as thick as conventional oils when it gets cold and will meet the 5W30 specification without additives. In order to get conventional 30 weight oil to thin out when cold it is necessary to add viscosity improvers. The VI has been a disaster in some of the hot running car engines. Note that some now will not warranty an engine if you use 10W40 conventional oil. I saw one engine where the rings were froze into the pistons due to the VI. It was necessary to throw the pistons away.
The first number "5" means at 32F the oil has the same viscosity as straight weight 5 at 32F. The 30 means that at 212F it has the same viscosity as straight weight 30 at 212F. So when cold it is still thicker than it is when it gets hot.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Good Post but you have it backwards They start with the low no. base oil 5W then add Polymers which prevent the oil from thinning as much as it warms up 10W-40 and 5W-30 require a lot of polymers polymers can shear and burn forming deposits and frozen rings as you say among other things The wide range oils are more prone to viscosity and thermal breakdown due to the high polymer content And leave you with the base oil You wouldn't put single grade 5w in would you So when it breaks down you have 5W base not 30W
10W-40 IS Well know to do this and As you said Very few manufacturers recommend 10W-40 any more and some threaten to void warranties if it is used So the other post that said 10W-40 is probably better is flat wrong 20W-50 is the same 30 point spread But has less polymers
Spud
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
spud2004 wrote:

the polymers used for multi grade are elongated and kind of curl up as they get cold.
When Mobil 1 first came out I was having oil problems when pulling a trailer over high mountain passes. Even with 20W50, I would be down almost a pint or more after going over a high pass. When I would open the filler cap fumes would come out. I decided to give the Mobil 1 (only came in 5W20 at that time) a try. Much to my amazement my oil usage essentially disappeared. My theory is that engine was running so hot it was vaporizing the oil.
I read where it takes about twice as much polymers to make 10W40 as it does 10W30. It caused a lot of stuck rings in hot running engines.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Rich256 wrote: ..

I am not sure, but I believe that is backwards. I believe the viscosity improvers make thicker than it would be otherwise when it is warm.

That part is certainly right. Why is it that so many people get that part backwards?
--
Joseph Meehan

Dia \'s Muire duit
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.