Q: To upgrade or not to upgrade... MacBook Pro Late 2008?

Technically it is possible, but is there any particular reason that you feel the need to upgrade? If your current setup isn't working well, upgrading it to a new system probably won't solve that (or make it worse).

At the very least begin downloading OS X El Capitan so it's available as a previous purchase to have in the future.  When Mac OS Sierra becomes public then OS X El Capitan may not be available as an free upgrade--since this is what happened with previous versions.

Whether or not to install OS X El Capitan depends on you.  Do you need new features that are unavailable in Mavericks or do you need to use software that requires a later version of OS X than Mavericks?

I would recommend creating a Time Machine backup first.  If you do not like OS X El Capitan or there are compatibility issues with third party software you can do a complete system restore with Time Machine.

Use Time Machine to back up or restore your Mac - Apple Support

The need to create an external archive backup of your content is an idea that

could help you in the future, even if you do not upgrade to a newer OS X soon.

A limited amount of free or unused capacity in the hard drive is an indicator that

you should do something about moving older items you may want to keep, off

of the hard drive; then trash or delete the originals from the MacBook HD to free

up some working capacity. This can help, to have more working space in the HDD.

Another item would be to upgrade the memory chips, you'd do that through purchase

of two new larger capacity ones; then the computer should work better in Mav 10.9.5

and also in any subsequent system upgrade. One of my computers runs Mavericks

10.9.5 & I upgraded RAM from 4GB total, to 16GB total (two chips) to be ready for a

system upgrade; hardware should be able to support a later OS X, before you try it.

You can see what kinds of upgrade parts are available from this company page:

https://eshop.macsales.com/MyOWC/  they also have replacement batteries, etc.

With one of my older MacBooks, the hard disk drive was upgraded to a faster rotational

7200-RPM drive of larger storage capacity, & both RAM chips replaced. It runs very well.

However it is old enough to not support the latest version OS X or newer apps.

In any event...

Good luck & happy computing!

You have had good replies.

One remark about the Ram:

Early 2008 MBP, model 4.1, 15": can handle max 6GB (667MHz)

Early 2008 MBP, model 4.1, 17": can handle max 6GB (667Mhz)

Late 2008 MBP, model 5.1, 15": can handle max 8GB (1967MHz)  <----

Late 2008 MBP, model 4.1, 17": can handle max 6GB  (1067MHz) <----

Early 2009 MBP, model 5.2, 17": can handle max 8GB (1067MHz)

As you have the late 2008 it is not clear if you have the 15" or the 17".

To upgrade Ram is cheap and easy: just put in two 4GB modules and 6 or 8GB is handled depending which model you have.

Make sure to buy a good brand with the exact specs. See Crucial or OWC.

Lex

OK, forget about upgrading for now and focus on the current issues.

Several things you can do. Caches get cleaned out when you do a reboot in Safe Mode, followed by a normal boot: Try safe mode if your Mac doesn't finish starting up - Apple Support

For the hunt on large files, Omnidisk Sweeper is a good start: https://www.omnigroup.com/more

Then there's the trackpad issues: see the helpful suggestions by Linc Davis in Trackpad on mac book is going crazy!

For possible software conflicts or incompatibilities you can post a Etrecheck report: http://etrecheck.com

Sometimes odd things happen, when the internal battery starts to go bad or has

swollen up; as this presses on the underside of the keyboard and trackpad...

And so if this has happened, the internal battery would need replaced. -- If not, a

few other things may be causing the odd behavior with the trackpad & hardware.

The hard disk drive storage capacity is generally not referred to as 'memory' while

the RAM (random access memory) is the real deal. So I assume in the matter you

are referring to the increasingly-full hard disk drive; even though the RAM or memory

chip capacity is something that could see upgrade w/ new chips to help performance.

A MacBook Pro (15-inch, Late 2008 mode)l is also referred to as MacBookPro5.1;

While the 17-inch, Late 2008 model is referred to as MacBookPro4.1; along with

a few other identifiers to help be more precise in knowing the exact model build.

{The total RAM memory capacity is actually higher than original Apple specs, btw.}

If your MacBook Pro is a 15-inch model, Late 2008, the maximum memory chip RAM

upgrade capacity is more than the 17-inch model Late 2008. According to Mactracker.

Maximum Memory    8.0 GB (Actual) 4.0 GB (Apple)

Memory Slots    2 - 204-pin PC3-8500 (1066 MHz) DDR3 SO-DIMM

The MacBookPro 17-inch Late 2008 model can use a less capacity in memory RAM

and the computer also uses a different part number series; note the numbers do not

interchange with the 15-inch Late 2008. They are of different physical specification.

Maximum Memory   6.0 GB (Actual) 4.0 GB (Apple)

Memory Slots    2 - 200-pin PC2-5300 (667MHz) DDR2 SO-DIMM

Above specifications taken from http://mactracker.ca database app for reference.

• MacBook Pro: How to remove or install memory - Apple Support

It would appear if you have the 15-inch MacBook Pro Late 2008, it is a newer design.

Faster speed memory chips, different pin count, later build; newer type hardware, etc.

However before any hardware upgrade (to run present system at better performance)

the unit you have, should be fully properly identified so you are looking at correct parts.

The OWC page link given earlier can be used to get an idea of replacement parts to

upgrade the hardware; this could be helpful to solve problems before considering a

newer OS X which would also bring with it more demand on system resources.

An idea may be to take the computer to an Apple Store with Genius, contact them ahead

of time to see when you could get an appointment; if no Genius or official Store is available

then consider discussion of the issues and upgrade (hardware) with an AASP since an

Apple Authorized Service Provider can give you estimates on the cost to you, if they do it.

You can upgrade the parts yourself by ordering from OWC macsales and use their online

video to install; or see the iFixit.com repair guides for MacBook Pro. Not too hard.

As it appears I have more information than you can use at this time, consider the options

and identify the computer more accurately. You could use any number of resources.

• Mac Serial Number Lookup - identify your Mac:

https://www.powerbookmedic.com/identify-mac-serial.php

Enter the SN of computer in the line, to see what it says. I already know what it can be.

That site also shows a variety of parts and may have some instructions on replacement.

Also everymac.com has significant information about most things Mac; specifications of

most all Mac computers are on their site.

Not sure what else to say; if an expert suggests a diagnostic to test the hardware, that

may or may not be sufficient; a Genius may check it over for free; otherwise there's a fee.

If there is another issue inviting a repair, that does not involve new hard drive, or RAM chip

upgrade, the overall costs may start to be prohibitive; unless you can do the parts upgrade.

Good luck in this matter!

Noticed a minor error in the specifications you cited; as I was editing my reply

and chose to not add a ton of other stuff knowing the identity of the MB/Pro is

an unknown at this point...

{Both of these are typo; MHz specs are technically incorrect; this is to inform the thread author.}

I did not see the other replies when I began the second reply... as I researched

plenty and rehashed what I already knew against the sites I have bookmarked.

And the time is getting late/early here; only 1:20AM Monday AKDT.

In any event...

Good luck!

K : Yes 1967 should be 1067. sorry about that but it will not cause any uncertainty I suppose.

btw; 1066 is "equal" to 1067, all depending to the source that you look at.

The GB's are correct: the 17" is a 6GB max.

Yes: the 15-inch MacBookPro5.1 Late 2008 uses this or near equivalent:

And: the 17-inch MacBookPro4.1 Late 2008 uses this or near equivalent:

The pin count is different, data rate/speed, and part build series, is too.

As saga goes, without an exact identification of main product, we guess.

And at 2:55 AM I should have been sleeping instead of living this nightmare...

That is why you should order it from OWC or Crucial: you find it by identifying your mac model.

and yes the 1067 should be 667, that was a typo also. correct. like your 16GB...

However 'my' 16GB references a different model that actually does use

that capacity RAM; and to avoid any confusion, all of my replies with the

cited MacTracker supported specification are underlined.

The fact the most recent Mini I have and use runs Mavericks 10.9.5; shipped

with 4GB RAM (and dual 1-TB HDDs) now has 16GB in 2- 8GB chips -- has

little to do with the MacBook Pro Late 2008. Except the upgrade helps 10.9.5.

[+ My old MacBook1.1 1.83GHz saw upgrade to fast/larger rotational HDD, w/

more RAM (667MHz, 2GB total) is quite a boost. At least compared to 512MB

and original small slower HDD. But it still only can use up to 10.6.8.]

As a matter of fact... in fact.

A redundancy, just now repeated with more detail.

Like I tell my 86 y/o parent for whom I care daily.

with Memory 4GB

Upgrade to the maximum for your model, 6 or 8 GBs. 4 GBs is marginal, even if you don't upgrade anything else.

I have 26.41 GB Free out of 249.2 GB on the HD

Not much free space, if you have the original 5400 rpm hard drive, upgrade to a SSD, probably 500 GBs, given the amount of your current free space. (This would be your biggest performance improvement)

Can I upgrade to El Capitan?

Yes

Should I upgrade to El Capitan?

Yes