Engine oil viscosity - swings and roundabout?

[Dave the tram]

Although my GT6 engine seems ok for now, possibly a bit tired but runs well and no nasty smoke etc, I’d become a bit anxious about low oil pressure on long hard journeys, especially in hot weather. When cold  I was getting 65psi at 2k revs and not that much less at tickover, but when fully hot on a long journey it was about 30 at 2k and less than 10 at tickover which worried me. I switched to Millers sport 20/60 oil and noticed an improvement in pressure so never less than 15 at tickover when very hot - but am I kidding myself?  The gauge gives reassurance but is the lubrication really better as it will need more pressure to get thicker oil where it’s needed (bit like narrowed arteries, high blood pressure and blood thinners). The thing that really makes me question things is that I now get a start up rattle, whereas I didn’t used to with standard oil. Although the cold viscosity figures for the oils used are both 20, I suspect that the millers is taking longer to get round and the pressure gauge is slower to climb. I have always had a spin on filter that should help retain oil for startup. I now daren’t  touch the throttle and keep the choke in as much as possible until the gauge has climbed and the rattle gone. I might switch back to previous oil in case I’m doing more harm than good, and just keep saving up for that eventual engine rebuild one day. Any thoughts on this theory about oils?

Cheers

Dave

[dougbgt6]

Dave,

Blood thinners! Tell me about it!

My oil drops 20 psi from cold to hot, 10 at tick over ain't really bad.  Mines 20, hot, but you can't really trust gauges, they're only there to tell you if it's the same as yesterday. Also my pressure went down 5psi when I swapped from Duckhams to Millers!

The death rattle is always with us, the oil retention capability of the cartridge filter depends on a crude plastic (?) flap and can be variable from cartridge to cartridge. They can also fail. I would say your oil and/or your cartridge have had it rather than your engine.

Doug

[johny]

Wow a rather complex and emotive  topic! Only things to add are that obviously the cooler running your engine the less thin the oil gets. Starting rattle gets worse as oil pump and crank bearing clearances increase. For the first Ive put in a new radiator and for the second new bearings and oil pump both of which have helped a lot....

[Pete Lewis]

did you change the filter when you changed the oil ??

its worth checking thePRV is clean and not harouring a small bit of debris 

the rattle is a normal event  and apart from good and bad filters (do you have a spin on or side mounted std)  there is also gallery drain as the oil in the gallery and journals will 

drip back to the sump over a period just due to gravity  , drain back is not purely the filter 

Pete

[Steve P]

Never any start up rattles on my Vitesse, instant pressure and good pressure once hot, fwiw i use a Fram filter at about 45 degrees with the spin on conversion and VR1 oil.

Others will have their own opinions.

Steve

[johny]

Yes definitely not obligatory to have rattle on start so I think it depends on engine condition, choke adjustment which controls initial revs, oil filter and maybe factor X🤗 

[Clive]

If a spin on filter is used, it is possible to get one wit a non return vanve on the inlet and outlet. So can't drain either way. But I have found teh millers oil to be excellent. 

It may be that your bearings are worn, but simply replacing them may well improve things considerably. 

I have heard that Penrite oil is very "sticky" so if you are concerned that may be worth a try. 

[PeteH]

The "trick" Back when, was to use Molyslip additives. Thinking being the moly gave the bearings some "Lubrication" before the oil got there.

Pete

[johny]

As I think weve said before dont think a bit of rattle is too disasterous and engines can go on for quite a few more miles with it. However its not ideal and obviously revs should be kept to a minimum until the oil arrives👍

[daverclasper]

I always crank without choke, until light goes out and no rattle (used to rattle loud for a sec, or two, until I did this).

It even rattles quite loud for a split sec after running, if started after a couple of hours and the revs are bit high on start up? (never heard this mentioned anywhere before?). Have spin on filter.

Oil pressure (on gauge?) is good and has been consistent for 20,000 miles. Don't drive car hard, so try not too worry too much? 

[Dave the tram]

Thanks for all the comments. To clarify, I do have a spin on filter, did change the filter with the oil and usually change both every year or 3 k whichever comes first. I start it with minimal choke and revs until pressure built up. The main point is that I had very little start rattle with previous oil (just Halfords classic 20/50 or later Castrol Classic 20/50) and the rattle became noticeable immediately after switching to Millers, at the same time as the hot pressure improved. Once I’ve used the batch of Millers I have, perhaps I’ll switch back on the basis that 8 psi at very hot tickover once in a while is doing less harm than an avoidable rattle at every start up.

Regarding the final response, I won’t let it worry me as I have a little savings pot for an eventual engine rebuild and will go on enjoying the car daily - but this will of necessity involve some ‘hard driving’ - it’s a sports car and great to drive!

Cheers

Dave

[rlubikey]

16 hours ago, daverclasper said:

I always crank without choke, until light goes out

+1 for that.

Cheers, Richard

[Dave the tram]

Also, I have a fairly new radiator with extra core, new pump, thermostat and hoses and the water temperature remains as is should be regardless of driving and conditions, so actual overheating not a factor just hot oil after a long hot drive.

Dave

[Bfg]

On 20/10/2022 at 13:38, Dave the tram said:

I now daren’t  touch the throttle and keep the choke in as much as possible until the gauge has climbed and the rattle gone.

 

On 20/10/2022 at 19:35, johny said:

obviously revs should be kept to a minimum until the oil arrives

 

These sound contrary to what I understand to be good practice, which is to start and run the engine with a brisk tickover (but not racing).  The engine is not under load. 

A slow tick-over will not help your oil-pump get the flow of oil to where it is needed and will increase the engine's warming up time. 

Multi-grade oils of 20/50 or 20/60 are suitable for very much colder winter conditions than you ought to be experiencing in the Peak District at this time of year.  Its low temperature viscousity would not prevent flow and cause a rattle.  However.., I am not sure about the Miller's Sport which is a semi-synthetic and blended "with enhanced performance additives and shear viscosity improvers to deliver higher protection at competition temperatures. "   

Perhaps you might give Miller's a call and ask what they think. 

Pete

p.s. I'm using Penrite's Classic Medium (high-zinc mineral) oil in my old TR4 ..and that's 25w/70.  Despite the engine's long stroke characteristics (and crude design origins) it doesn't have a start-up rattle ..but then I wouldn't run the engine slowly when cold.  When hot soaked (after a run and then stopped in traffic lights) at slow tickover (about 600 rpm) the oil pressure gauge drops to read 35-psi or so, but the oil warning light I fitted doesn't flicker.   Personally I now only use Halford's classic 20/50 as a flushing oil. 

[johny]

27 minutes ago, Bfg said:

 

 

These sound contrary to what I understand to be good practice, which is to start and run the engine with a brisk tickover (not racing).  The engine is not under load.  A slow tick-over will not help your oil-pump get the flow of oil to where it is needed and will increase the engine's warming up time. 

I think the recommendation is to drive off and warm up the engine on the move. Certainly the higher the idle speed setting of the choke the worse any rattle is likely to be and it brings tears to my ears....

[NonMember]

2 hours ago, Bfg said:

These sound contrary to what I understand to be good practice, which is to start and run the engine with a brisk tickover (not racing).

Not really. The advice to keep revs moderate and load low is, as johny says, part of the "drive off and warm up on the move" advice. It's all about what you do in general from start+10seconds until it's warm. The Triumph six "death rattle" happens during that first ten seconds. However, the point about slow tickover delaying the oil pressure build up is entirely fair. The bearings are not working any harder at 1500RPM idle than they are at 750RPM idle, but the oil pump is doing its job much better.

[johny]

Sounds like between a rock and a hard place and each has to decide on their own preferred method🤔

[PeteH]

A lot, not necessarily Triumph cars of this vintage, rattle a bit on startup. especially if left for any period between use`s. I suspect "we" have just got used to more modern vehicles with their closer tolerances. I had a "modern" (well 15+ year old) which had done well over 150K miles and still the Oil light went out after a matter of milliseconds on startup. The engine had never been touched, beyond Oil/filter changes. To properly check Oil Pressure, you really need to fit a Certified Prssure gauge into the Oil system, In car instuments can be notoriously fickle.

For those who remember such things, Many old "brit" bikes would drain the contents of the Lub tank to the sump if left to long. Tech; has moved on since then!.

Back in the day, we de-coked engines at what are regarded (now) as very low milages, often doing major work on engines with less that 100K. Ford "pinto`s" for example, used to eat valve seals in very short order, you always knew, puff of blue smoke as they left the traffic lights!. in theory that was a head off job, in practice they could be changed in situ.

Pete

 

[johny]

Suppose it comes down to deciding between a nice fast cold idle setting but possible increased horrible rattle on start or minimise the tickover on the choke cam/knob to reduce it as much as possible....

 

[NonMember]

25 minutes ago, johny said:

Suppose it comes down to deciding between

Well, unless you're going to go the Marcus way and fit a pressurised oil reservoir to prime the system before cranking. Most of us consider that overkill.

[Pete Lewis]

well its been knocking for 50 years  dont get paranoid about it 

clearances are such that being old design you hear it on a modern you dont 

a light ruuning engine on fast idle will not wreck istelf on the first few seconds of rumble 

if it did we would not have any triumphs to play with now would  we 

yes its a rumble but its not a death rattle 

learn to live with it it will see most of us out if they last another %^&*( years 

a spin on filter has the advantage of easier servicing  its not the be all and end all of an empty oli filter and the  gallery 

when stood still for a week or more 

fire it up daily if you can and the rumble wont happen 

in their day as a daily driver it never occured 

Pete

[Dave the tram]

Good discussion. I’m going to take a middle road for those first five seconds, just enough revs to get the oil round quickly, then drive off. It’s off the road for its respray etc but normally gets very regular use which is good for it. Think I will go back to a good 20/50 next oil change instead of the Millers cos I’m sure the rattle only became noticeable when I switched to it in order to get better pressure at tick-over when very hot.

Talk about de-coking old cars quite often - my Dad had cars in the 1930s (must be in the blood) - I realise now that very few people did - and used to talk about taking the head off old side valve engines and de-coking MOST WEEKENDS! I remember him when I was a small lad digging a full size inspection pit through clay before laying the concrete floor to build his garage. A true home mechanic.

Cheers

Dave

[Chris A]

16 minutes ago, Dave the tram said:

I’m going to take a middle road for those first five seconds, just enough revs to get the oil round quickly, then drive off

That's basically what I do, start it, enough choke to keep it running, fit seat belt, open gates (electric so can do it from car) then gentle driving until engine is warm(ish) and no choke.

[Pete Lewis]

so back we go to injecting vast quantities of Redex down the carb throat 

followed by a cloud of thick white smoke you could have seen from space   

Happy days 

did it remove carbon...no idea.................but it sure wound the neigbours up 

Pete

 

[Bfg]

Just now, johny said:

I think the recommendation is to drive off and warm up the engine on the move. Certainly the higher the idle speed setting of the choke the worse any rattle is likely to be and it brings tears to my ears....

"driving off and warming the engine on the move"  ..Is this not the case for modern / post mid 70's engines ? ..whose designs moved more towards oil-flow,  in preference to the emphasis on oil-under steady pressure of more traditional automotive engines (which sought to float journals on their bearings). 

I am unfamiliar with Triumph's six, possibly it was designed during the design transition from one to the other ?  Might I ask where its commonplace start-up (aka death) rattle comes from.?  Knowing that would help determine which oil and start up / tick over revs might be best.

I ask this because the early Jaguar straight sixes (whose design is founded in late 1940's) had a reputation for cold-engine rattles from one or more of the valve guides being loose. Bolt-on clamps are the usual remedy, which hold the guides tight until the engine's tolerances tighten as the engine warmed. Clearly this was not an oil pressure issue but one of the thermal expansion rates of different component materials. 

Of course our conversation may be at cross purposes if one's understanding of a brisk  tick-over is different to another persons.  For clarity, on my old Standard Vanguard 4-cylinder / tractor / TR4 engine - I've now set the hot tick-over to around about 600 rpm, and so my "brisk" is 1000-1200 rpm. 

NB. When I bought the car, it was higher because the carbs were unevenly choked and any less rattled the whole car.  Cold tick-over had been adjusted to be around 1500 revs and heavily choked too.  The pull lever / rod mechanism was badly adjusted and so the choke was either on or off.  Without the lever holding half or quarter choke settings - the engine wanting to stall when I put the choke-in within the first mile or two. I've since adjusted that to lessen the amount of choke (enrichment) throughout the cold start range ..so as not to foul the combustion chambers &/or exhaust up, and I've better balanced the activation mechanism so more travel of the pull knob is required to achieve full choke.  In short ; the more travel give me a finer increments of adjustment, and allows those mid position (1/2 and 1/4) settings.   

I push the car out of its car-port/ poly-tunnel, and then warm the engine at tick-over for a few minutes before driving off, not least because I live on a hill, and prefer not to slog a cold engine up it.  In practice this usually means starting the engine (once it's out of the car port) and then closing the house and poly-tunnel up, setting the GPS's route and getting myself settled with belt, bobble hat and scarf on.  Conversely, in my modern (a 20 year old Chrysler Voyager) which lives out in all weathers, I just get in and go. I drive gently and in a low gear, but still it takes a tenth of the time to get to the local shop. 

My old Sunbeam motorcycle (1950's ohc in-line twin) - I kick the engine over two or three times without the ignition on ..to pump the oil and to prime the fuel in the combustion chamber, and then start it.  Again I set a brisk tickover, with a minimal amount of choke ..before leisurely donning my helmet and gloves, etc.  Again I ride off gently and in lower gear so as to not slog the engine. Unless it's literally freezing, it only takes a mile before the choke can be set all the way in. 

 

Just now, Pete Lewis said:

when stood still for a week or more 

fire it up daily if you can and the rumble wont happen 

Again ..as I understand it, this is not good practice - because starting up ..without then thoroughly warming the whole engine and gearbox through just fills them, and also the exhaust boxes, with condensation.  Even after ticking-over for a few minutes before setting off - it takes a number of miles for these engines to warm through and for all the condensation to evaporate and be vented out. Those miles are also required to burn away the soot, from where the choke has been on, rather than it just being blown into the exhaust.

Pete