TheSamba.com :: View topic - What would be your temp limit for a long road trip?

Fri Jul 19, 2024 9:52 am

I mechanically savy and know how to prepare for a long road trip with no a/c in hot weather. Assuming I pickup a sound 61-67 that doesn't have an oil cooler what would you say the peak temps you would consider for a long road trip with significant highway miles (but at possibly reduced speeds 60ish).

**more focused on where these air cooled motors start to get overwhelmed by ambient temps than your personal traveling preference***

I realize you deal with other issues once you stop too as carbs can boil. I have a phenolic spacer on my 60s Dodge and it made a world of difference with boiling/vapor lock.

So far no end in sight for the heat I am seeing out west and I likely see some big elevation changes in my travels.

Fri Jul 19, 2024 10:30 am

If your VW has all the tin and good sealing rubber, I'd just use "the tennis ball trick" to keep the engine lid up a few inches on highway.

No one's temperature sender/gauge is calibrated, and depending upon which unit you use, and WHERE in the oil path you mount it will affect your readings.

Myself - I've had an oil temperature gauge since 1976, and its primarily use is to let me know if oil temperatures rise higher than I normally get. By the way: I run 1835cc DP engine, in Arizona desert. And have made quite a few cross-desert, mid-summer, mid-day trips to California and back. However, due to now owning Nissan Frontiers and a Yukon with real AC, those would make such desert crossings....

Fri Jul 19, 2024 12:14 pm

This is from VW.

To Cussers point, I'd make sure all the engine tin is in place so hot air can't get into the engine compartment from under the engine.
Then make sure the engine timing is set correctly. Too much timing equals hot temps. If you're driving on the freeway, stick to 60 mph.

I drove a bug through the desert in summer time several decades ago. I just kept my speed down, made sure the timing was correct and the oil was full. The only issue I had was I was too hot! :wink:

Fri Jul 19, 2024 1:35 pm

Make sure that all the motor's adjustments are spot-on and be sure to check the oil level at every fuel stop, especially if this car is new to you and you're not familiar with its habits. Keep the tires properly inflated too.

If you cruise along in the 55-65MPH range, you'll be fine. During WWII, the Kubelwagen was capable of off-roading thru the North African deserts without overheating. At least you should be on paved roads all the way 8)

Fri Jul 19, 2024 3:20 pm

I sure hope your Bug has an oil cooler!!!! (they all had them factory fitted!!!)

I have driven my Bug in 115F heat, no problem. My granddad drove his 1965 Bug all over Arizona for decades, He even loaded the engine down with an air conditioner, thus making the engine work even harder. His Bug ran fine.

Fri Jul 19, 2024 4:25 pm

I just did a 2-hour drive in 114F heat. I wasn't worried about the engine; I was concerned about myself. It's not bad when it's 105 F out, with the window vents open, but 114 F is like having a hair dryer blasting my face—so, 114F, 218F oil temp (checked with a meat thermometer), 30 weight oil.

Fri Jul 19, 2024 4:56 pm

KingAir42 wrote: I just did a 2-hour drive in 114F heat.

:lol:

Sat Jul 20, 2024 8:09 am

240-250°

Buy a IR gun of you don’t have a temp guage. I use 20/50 in the summer months. Tennis ball trick is good, VS sells a stand off that does the same thing as the ball for a reasonable price.

https://store.vintagespeed.com.tw/1965~1967-BUG-ENGINE-LID-EXTENSION-p108809664

https://www.homedepot.com/p/RYOBI-8-in-Infrared-Thermometer-IR002/205509667

Sat Jul 20, 2024 12:09 pm

The engine is not the problem.

The question is what temp YOU start to fall out. The car will be fine (assuming of course your cooling system is intact, which includes all tin and the rubber seal between the tin and body).

Sat Jul 20, 2024 3:59 pm

I can drive the freeway in 90+ degree heat here in Houston, TX. That's 50 miles and the car will sit below 220.

Fri Jul 26, 2024 3:04 am

richparker wrote: 240-250°
richparker wrote: I use 20/50 in the summer months. This is why your oil temps are so high. Use 5 or 10W-30 and your oil temps will be a LOT lower.

Wed Jul 31, 2024 6:16 am

Bruce wrote: richparker wrote: 240-250°
richparker wrote: I use 20/50 in the summer months. This is why your oil temps are so high. Use 5 or 10W-30 and your oil temps will be a LOT lower.

Every engine is different. I’ve had ones that like 10/30, the current engine in my beetle likes 20/50.

Wed Jul 31, 2024 8:00 am

I have seen such varying temps between cars, I don't trust the absolute values on any temp gauge anymore.

My rule is "10 degrees hotter than the usual reading under similar conditions" is the tipping point where I will immediately slow down, and if necessary pull over to see if timing or other settings have slipped.

Wed Jul 31, 2024 11:30 pm

richparker wrote: Bruce wrote: richparker wrote: 240-250°
richparker wrote: I use 20/50 in the summer months. This is why your oil temps are so high. Use 5 or 10W-30 and your oil temps will be a LOT lower.

Every engine is different. I’ve had ones that like 10/30, the current engine in my beetle likes 20/50.
At 250°F, your current engine is telling you 20W-50 is too thick.

Fri Aug 02, 2024 7:12 am

Bruce wrote: richparker wrote: Bruce wrote: richparker wrote: 240-250°
richparker wrote: I use 20/50 in the summer months. This is why your oil temps are so high. Use 5 or 10W-30 and your oil temps will be a LOT lower.

Every engine is different. I’ve had ones that like 10/30, the current engine in my beetle likes 20/50.
At 250°F, your current engine is telling you 20W-50 is too thick.

Ok, you win.

The OP question was “temp limit,” not normal operating temp. 🙄

Sun Aug 04, 2024 3:08 pm

250°F is not a normal operating temp.

When you use 20W-50 tar, it causes higher oil pressure than if you use thinner oil. That higher oil pressure causes the oil to bypass the oil cooler. By lowering the oil pressure, you will make the oil go through the oil cooler, resulting in lower oil temps.

A friend used to have a mid 80s 911. It was one of the few cars on the market with an oil temp gauge fitted from the factory. In the owner's manual, it states the max temp limit at 230°F. If you change your driving when oil gets that hot, it's possible to never need to exceed that limit.
Some will point out that a 911 engine isn't the same as a VW engine. Irrelevant. Porsche oil is the same as VW oil. It's the limit of the lubricant that is of concern.

Sun Aug 04, 2024 8:09 pm

Bruce wrote: 250°F is not a normal operating temp.

When you use 20W-50 tar, it causes higher oil pressure than if you use thinner oil. That higher oil pressure causes the oil to bypass the oil cooler. By lowering the oil pressure, you will make the oil go through the oil cooler, resulting in lower oil temps.

I've mentioned before that I ran a 10W-40 in a freshly overhauled bug engine years ago before I knew better. I had higher oil temps than I liked. I dropped to 10W-30 and the oil temps dropped 10°. I can't imagine what the oil temps would have been had a ran a thicker grade of oil.

Quote- The oil pressure relief valve is located at the pulley end of the engine, near the oil pump. When the oil is cold and thick, the resulting increased oil pressure forces the valve down against spring tension. This allows oil from the oil pump to go directly to the engine bearings. In by-passing the oil cooler, warm-up is speeded and the oil cooler is protected against excessive pressures that might cause it to burst.

There was a great thread on TS a few years back that really delved deep into this subject of too thick of oil and high oil pressure. It reinforced that the thick oil and high oil pressure bypassed the oil cooler and you got higher oil temps.

Sun Aug 04, 2024 9:03 pm

Bruce wrote: 250°F is not a normal operating temp.

When you use 20W-50 tar, it causes higher oil pressure than if you use thinner oil. That higher oil pressure causes the oil to bypass the oil cooler. By lowering the oil pressure, you will make the oil go through the oil cooler, resulting in lower oil temps.

A friend used to have a mid 80s 911. It was one of the few cars on the market with an oil temp gauge fitted from the factory. In the owner's manual, it states the max temp limit at 230°F. If you change your driving when oil gets that hot, it's possible to never need to exceed that limit.
Some will point out that a 911 engine isn't the same as a VW engine. Irrelevant. Porsche oil is the same as VW oil. It's the limit of the lubricant that is of concern.

Bruce, obviously 250° is not normal operating temperature. The OP asked for the limit of temp. I feel 250° is the limit, others say ~230-240°.

180°-220° would be normal operating temperature. Which both of my ACVWs operate at.

Yes, the thicker oil does bypass the stock cooler. But, that’s only when the oil is cold, once it warms up and thins out it activates the plunger and goes through the stock cooler. I am not worried about this as both of my VWs are full flowed.

Again, my ACVWs do not operate at 250°. They operate between 180° and 220°. I do not have an issue with oil temps, I was simply answering the OPs question.

Mon Aug 05, 2024 3:59 am

richparker wrote: Bruce wrote: 250°F is not a normal operating temp.

Bruce, obviously 250° is not normal operating temperature. The OP asked for the limit of temp. I feel 250° is the limit, others say ~230-240°.

180°-220° would be normal operating temperature. Which both of my ACVWs operate at.

Then I disagree with your limit of 250°.

RIbeachbeetle wrote: ... what would you say the peak temps you would consider for a long road trip with significant highway miles ...

Mon Aug 05, 2024 8:40 pm

CAUTION: RANT AHEAD

Here are some relevant facts as a conversation piece.

1. You cannot really compare oil viscosity between or even within the same brand.

Reason: Oil viscosity standard is measured (usually) at 40 degrees C and 100 degrees C. In between these temperatures there will be a viscosity curve that most manufacturers would have but not necessarily publish. So going from say a Shell 10W50 to a Mobil 10W50 may both have the same viscosity at 40 and 100 degrees but could be completely different at the normal operating temperature of your vehicle.

Similarly the viscosity of one brand's 10W40 and another's 10W50 may in fact be "thicker" (higher viscosity) for the apparent "thinner" oil at the VW operating temperature. They only have to agree at 40 and 100 degrees C. We don't have their viscosity curves, but there is plenty of literature to show comparisons between oil viscosity,, by brand and at temperature on the net. This depends on the formulation of the two oils.

2. Positive displacement pumps i.e. a VW oil pump (gear pump) will actually pump MORE oil at higher viscosity than at lower viscosity, even though these are "thicker". This is opposite to a centifugal pump and counterintuitive to most people.

Reason: The higher the viscosity the less slippage there is back through the oil (gear) pump. So pumping MORE oil at start up to the bearings is a good thing. And the pressure will be higher so the bearings will be well fed with lubrication. Yes there may be a period of cooler bypass but that means the oil will be fed to where it is needed most and where the start-up wear is the greatest: the crankshaft and camshaft bearings.

3. Oil viscosity is not like water and treacle. There isn't much difference between the viscosity of 5,10 or even 50 grade.

Comment: Oils today have lots of viscosity modifers and other ingredients. When you pour oil from a bottle at room temperature it will have little bearing on what the apparent "thickness" appearance inside the engine is at 200F. Few can ignore how thin an oil is when draining the sump after heating the car up prior to an oil change.

4. The VW Service document of 1957 is probably irrelevant today as are the temperature profiles recommended.

Reason: The oils used in those days and what these temperatures were based on were probably for straight cut 30 motor oil, with none of the technical advancements of oil we have today. The reason that the temperatures were recommended was more because the mineral oil of the day broke down more readily at higher temperatures than multigrade oils of today. This is the main reason that engine failures happened. The old oils would rapidly deconstruct and lose their ability to provide lubrication compared to the oils of today. Very frequent oil changes were a testament to this.

5. Whilst I have no doubt that some people think they can see a temperature difference by using a different oil I fear some of this is subjective not objective.

Reason: 1. Uncalibrated temperature gauges. Most of the gauge sets I see people using have a very poor temperature resolution at operating temperature. That is, many people have to interpolate between two temperature readings.I wonder if 10 or 20 degrees is even accurate to read?

Reason 2: My gauge versus your gauge? Unless calibrated to a standard it is unlikely to be able to be compared between set-ups. Yes even a candy thermometer or IR thermometer may not be enough to verify what's really happening in the motor.

Reason 3. Cooling effect on any car is dependent on:

(a) air flow via the fan at a specific RPM.
(b) speed through air giving cooling of external engine parts by conduction and convection
(c) humidity and temperature of the day. Different humidity affects the ability of the cooler to remove heat as does the ambient temperature and wind chill effect.
(d) Whether all the seals and hoses and fans are operating like they were designed to do and whether the oil cooler is effective.

So even by changing from one grade of oil to another and claiming DEFINITIVELY that a car runs cooler or hotter is in my opinion subjective.

Finally to end my rant there is no doubt that some of the tricks etc that people use to help cooling such as the tennis ball trick, external coolers etc work well, I have reservations that if we did the experiments on different oil viscosity in a controlled fashion that we could really prove what temperature the 60+ year old cars can be safely driven at.