moving from 10w-40 to 5w-30. isit okay?

[Fredoops]

Www.bobistheoilguy.com
/thread

If Honda dealers in Florida, US (which is Townsville weather) safely uses 5w-20 in Hondas and Acuras, why would I want to use something that's 2.5 times as thick. Honda engines aren't detroit V8's, we don't have as much tolerances in there.

Thicker =/= better
Bitog forums has plenty of oil test results that shows that.

[Egcivicduty]

yes but the reason they run 20 weight is so they can report higher fuel consumption rates to the government, at a cost of engine life.
the engines were most likely designed to run sae30.
especially if you have a high revving engine, whilst it mightnt do serious damage, i wouldnt risk dipping under the ideal oil pressure of 10psi per 1000rpms

[Fredoops]

My k-series euro users manual doesnt even allow anything over 40. I'm sticking with 30 or 40 full synthetic.

[aaronng]

My k-series euro users manual doesnt even allow anything over 40. I'm sticking with 30 or 40 full synthetic.

Yeah, the last engine that specified a 50 weight oil in the manual was the f22a in the CD5 Accord if I remember correctly.

[TbM]

Reccomended oil for normal driving conditions for b18c5, should be roughly the same as the b18c7 iirc.

yes but the reason they run 20 weight is so they can report higher fuel consumption rates to the government, at a cost of engine life.
the engines were most likely designed to run sae30.
especially if you have a high revving engine, whilst it mightnt do serious damage, i wouldnt risk dipping under the ideal oil pressure of 10psi per 1000rpms

Using a lower weight oil will give you lower fuel comsumption readings not higher. Not every engines oil pressure should be 10 psi per 1000rpm. For example the k20a3 requires 44psi at 3000 rpm according to my service manual and the b18c5 requires 50 psi at 3000 rpm.

Heres detailed explanation of oils, long read but has heaps of info on the subject.
http://www.supramania.com/aehaas/index-2.html

[Egcivicduty]

I'm not sure of the exact details, what I meant is that a thinner oil gives a better fuel economy during the actual test the use for CAFE standards.
If a manufacturer fails to meet the standard they can face big fines. During one of the test the lower weight and shear friendly oils perform better, at least it's what I've heard. Let me know if you know differently.

the 10 psi thing.
I'ts not like its a set it stone rule.
http://www.positivespin.us/MotorOil.htm go here to read part 8. Lol taken from the exact same article as the supratech one.
I'll do my best to summarize
although the article is much better,

It's completely to do with your oil relief valve, and its probably safe to say its a theory.
I dont know exactly when it opens on a b16a, I did a search and found 70-75 :/ i dont think its correct, if anyone knows please tell me.
Well I expect it to be at least 80 when it opens, but lets see anyway. Lets say you have 15 psi per 1k rpm.
1k -> 15 psi
2k -> 30 psi
5k -> 75 psi
6k -> 90 psi
8k -> 120 psi
Oil relief valve opens before 6k and reduces flow drastically, the result being your engine revs from 6-8k with reduced lubrication

if you have 10 psi per 1k rpms
1k -> 10
4k -> 40
6k -> 60
7k -> 70
8k -> 80
the result being constant oil pressure and flow figures right up the scale
and I guess hondas with vtec deviate at the lower part of the scale, the reason being that extra oil pressure is required to engage vtec, right? after vtec engages pressure drops slightly

[IV73CI]

aww i knew it! the last page couple of posts were deleted! :P

ok lets keep it to the topic now ..

Royal purple is crap and makes the car sluggish.

Penrite, Mobil, Castrol Edge sports ftw!

[TbM]

I'm not sure of the exact details, what I meant is that a thinner oil gives a better fuel economy during the actual test the use for CAFE standards.
If a manufacturer fails to meet the standard they can face big fines. During one of the test the lower weight and shear friendly oils perform better, at least it's what I've heard. Let me know if you know differently.

the 10 psi thing.
I'ts not like its a set it stone rule.
http://www.positivespin.us/MotorOil.htm go here to read part 8. Lol taken from the exact same article as the supratech one.
I'll do my best to summarize
although the article is much better,

It's completely to do with your oil relief valve, and its probably safe to say its a theory.
I dont know exactly when it opens on a b16a, I did a search and found 70-75 :/ i dont think its correct, if anyone knows please tell me.
Well I expect it to be at least 80 when it opens, but lets see anyway. Lets say you have 15 psi per 1k rpm.
1k -> 15 psi
2k -> 30 psi
5k -> 75 psi
6k -> 90 psi
8k -> 120 psi
Oil relief valve opens before 6k and reduces flow drastically, the result being your engine revs from 6-8k with reduced lubrication

if you have 10 psi per 1k rpms
1k -> 10
4k -> 40
6k -> 60
7k -> 70
8k -> 80
the result being constant oil pressure and flow figures right up the scale
and I guess hondas with vtec deviate at the lower part of the scale, the reason being that extra oil pressure is required to engage vtec, right? after vtec engages pressure drops slightly

Yeh your correct in what your saying about thinner oils reducing fuel consumption but you typed it wrong the first time.
"the reason they run 20 weight is so they can report higher fuel consumption rates to the government, at a cost of engine life.the engines were most likely designed to run sae30."
It should be lower not higher fuel consumption. i dont know why they would want to report higher fuel consumption.

Lol i knew you were using the A E Hass article when you started talking about 10 psi per 1000 rpm. Its not an idea pressure for every engine its just a basic guide.

I was under the impression that changing oil weight and operating conditions(ie track cars with increased oil temps etc) would vary the pressure though the rpm range so i dont think its completely up to the relief valve but i could be mistaken, I thought the relief valve was mainly used to restrict the maximum oil pressure.

Dunno when the oil relief valve opens on the b16a but heres the service specs i could find on the b16a2.

[Egcivicduty]

lol, obviously I dont read what I write

thanks for the specs bro