Engine oil grade for 98 Accord

Dear experts,

I have a 98 Accord that has 80K on it. Last week
I went an independent deader to get my oil changed.
The technician told me that I should be filling 10-30
or 10-40 oil since my car has a lot of mileage on it.
He said these oil protects older engine better.
The car manual specified to use 5-30 and nothing
else. Is the technician right?

Thanks,
Eugene

 

At 80K? No, he is wrong.

 

He obviously doesn't know what he is talking about. I am sure the 1968 Ford
pickup truck that this mechanic drives could benefit from this thinking but
not your car

 

If the car is losing oil (over a litre per oil change) and it's summer,
switching to 10-30 on an older car may be a wise move. However, I'd
switch back to 5-30 for the winter.

Pars

 

if its burning a quart ever thousand miles, it wouldnt hurt to switch to
a 20w50.

 

I'd start slowly - 10W-40 or maybe 15W-40 - and then only if it's
really consuming 5W-30.

However - at that much mileage, maybe a 10W-30 "high mileage" oil
might be a better idea.

 

The 5W-30 should be OK. If you live where the temps never get below 20F
then 10W-30 is specified by Honda, in the service manual, as OK for a '98
Accord. Personally in warmish temps I'd prefer the 10W-30.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

iirc, i think the second figure is the one to worry about at higher
temps, not the first, so you'd want 5-40 or 5-50 at high temps. the
first # is relative viscosity when cold. but even then, if the oil is
thicker, for a close tolerance engine like a honda, it will only result
in more gas consumption because of energy wasted churning thicker oil.
as long as the oil films are not breaking down, they're fine. that's
why transmissions with "thin" a.t.f. can perform just as well as
transmissions with "thick" gear oil.

i have relatives in las vegas and regularly drive over to see them.
even in the height of summer, with the temperature nice & toasty, and on
all those long multi-mile full-throttle hills, my civic with 5-30 shows
zero signs of stress. gas consumption is measurably better with 5-30
vs. 10-30 too. fact is, 5-30 is a better oil - it has to be to support
the wider viscosity range.

 

It depends on the oil basestock. A 5W-30 is basically a basestock with a
"natural" range of say 5W-15 for a petro-base with additive to extend its
VI so that you get a 5W-30; an equivalent for 10W-30 would be a basestock
with 10W-22 or so extended to 10W-30. As the VI improver wears out you're
left wth an oil which is getting closer and closer to the basestock value.

As an example, before the current situation with synthetics, which have a
wider natural VI than petro-base, a 10W-30 could be obtained with a PAO
basestock and absolutely no VI improver at all; a 5W-30 synthetic still
required some VI improver to get there. The VI improver doesn't suddenly
disappear one day - it wears out gradually (cheaper ones wear out quicker).
I'd rather have an oil which has less, or no, VI improver which will retain
its basic characteristics over the oil change cycle.

The "waste" of energy due to churning between a SAE 5W-30 and 10W-30 is
negligible -- barely measureable -- and any savings easily cancelled out,
over a tank of gas, by a couple of stop-light accelerations. As for ATF,
metals/alloys are chosen according to the lubrication available and
auto-trans do seem to have a lower reliability.

See above for which is the better oil. From my POV if you don't need the
5W for your climate, why use it? Like anything else there's no "one size
fits all".

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

rheology is not my thing, but i thought "natural" oil base stock
behavior was "thick" when cold, "thin" when hot. the way i understand
it, a rating like "5w-30" implies a thinner oil when cold and thicker
when hot, an "unnatural" phenomenon only viscosity index improvers can
impart. if that's not correct, what's the deal on this and how does it
work?

i'm only going on experience with my civic. it's typically 2-3% better
economy with 5w-30 than with 10w-30. this is measured on multiple 600
mile runs to las vegas over the course of 5 years.

automatic transmissions "fail" because of clutches or valves, etc,
components stick boxes don't have, but in terms of actual gear wear?
no, they're real evenly matched.

cos it's higher quality but costs the same money, so why /not/ use it?

 

I would not present myself as a rheology expert but was a chemist,
specializing in petroleum and petrochemicals, in a former career and worked
in fuels & lubes labs. The "thick when hot" is only relative: a 5W-30 is
still thinner when hot than when it's cold... specifically it's classified
as thick as a straight SAE30 oil would be when at the same hot temp of
100°C.

Every oil, even petro-base has a naural VI (Viscosity Index) which is what
the XW-Y designation represents: naphthene based petro basestocks, which
used to be preferable for diesels due to high natural detergency, have very
low VI and are little used now; paraffin based petro basestocks can have
quite high VI, though they are predominantly straight-chain and wax at
relatively high temps; and of course, the true synthetics and GrpIII
hydrocracked basestocks have very high VI, are predominantly branched chain
paraffin and wax at relatively low temps.

Though I have no inside info, I believe the current Mobil1, even 5W-30,
with the Supersyn formula has no VI improver additives. The Supersyn
series of products are basically blending agents, rather than additives and
are high density PAOs with extremely high VI. Mobil appears to have traded
a bit of pour point loss against elimination of VI improver additives.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

thanks george!

here's what i don't understand. i once saw a demo for some vi
improvers, and it was fascinating to see viscosity /decrease/ with
temperature and vice versa. i understand what you say about base stocks
with naturally high viscosity indexes, i.e. ones that don't change much
with temperature, but as i understand it, most bases still thin with
increasing temp until the vi improvers are added, albeit some more than
others.

so, here's my question; why /wouldn't/ i want a lube with a low cool
temp viscosity and higher hot temp one? something that maintains very
similar viscosity vs. temperature is going to cost me more in gas,
particularly in cold weather, and is not necessarily going to offer the
same protection, right?

 

The fluid film is what keeps your bearings from touching things harder than
them and frying.
A thicker (higher viscosity) lube won't change the film thickness, and is
harder to pump, regardless of temperature.

 

whats your take on valvoline full synthetic? crap? better than regular?
almost as good as mobil1?

reason asking was i wanted to switch over to a synth on my 2003 suzuki
burgman 400 scooter. manual calls for 10w40 or 20w50. being in a hotter
clime with extended freeway riding, i decided to go with the 20w50.

and since its a scooter, it doesnt have a wet clutch or gears in the
crankcase that would be benefited by using a motorcycle-specific oil.

autozone only had 2 qts of mobil1 15w50, i needed 3. being the lazyass i
am, i just got 3 qts of valvoline 20w50. itll only be in there for 4000
miles, but i just want to feel i didint totally get ripped off.

 

Apart from the VI improver itself, everything decreases in viscosity
(thins) as temp is increased. High VI basestocks thin much less and in
fact can often meet SAE specs with no VI improver. VI improver is a
necessary evil - it has no lubricating properties at all... same with pour
point depressants used in petro-based basestocks. Then of course with
those additives, you also need anti-foaming agents. Basically less is
better if the basestock has good specs.

If they both have the same upper figure, i.e. xW-30, the only diference is
in the cold temp viscosity so hot running should be the same and there is
no risk of losing VI as a VI improver breaks down over time. If you don't
need the 5W for your climate, why use it? Take a look at what Honda
recommends for the S2000 and NSX - the last time I saw a chart at the
dealers, they still spec'd for10W-30, while all the other Hondas had a 5W
lower figure. Also, for the early 90s Integras the GSR model was spec'd
for 5W-30 only up to ambient temps of 32F and 10W-30 for anythuing above.
Things have changed but Honda did not have confidence in 5W-30 back then
for its performance models and AFAIK still doesn't for the very top
performance models now.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

Higher viscosity usually does mean a higher film strength and better load
bearing characteristics. That's why the newer lower viscosity lubes are so
dependant on anti-wear additives, e.g. the Honda recommended 5W-20.

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

Hmm, we had a discussion about this recently and Yu-Ping Wang, posts as
y_p_w, looked up the Valvoline MSDSs and noted that the valvoline 20W-50
was still a PAO, whereas their other grades were now hydro-treated petro
basestocks. See

Rgds, George Macdonald

"Just because they're paranoid doesn't mean you're not psychotic" - Who, me??

 

PAO good , right? i likes that kung PAO chicken...


spicy!

 

ok, thanks!

 

AFAIK, the only thing that VI improver does is reduce the temperature
induced thinning - i.e. it's impossible to increase viscosity as
temps increase. The 5W-30 (etc) just represents where the viscosity
is at 0°C (5W) and at 100°C (30).

Do you mean the number (5W/10W/20W/30/40/50) or do you mean the absolute
viscosity. Like I said, it's impossible to increase the absolute
viscosity as the temperature increases. The SAE's XW-YY scale is
nothing more than an abstraction relative to "straight weight" oils.
A 5W-30 oil doesn't actually increase in viscosity with temperature.